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React Native Documentation Update

Rachel Nabors

Rachel Nabors

Documentation Engineer at Facebook

Last year we conducted user interviews and sent out a survey to learn more about how and when people use the React Native docs. With the data and guidance gleaned from 24 interviews and over 3000 survey responses, we've been able to work to improve React Native's documentation, and we're excited to share that progress today:

Thank you so much to everyone who participated in the interviews, the survey, and our documentation efforts! Your collaboration makes this possible.

React Native Team Principles

Eli White

Eli White

Engineering Manager on React Native

The React Native team at Facebook is guided by principles that help determine how we prioritize our work on React Native. These principles represent our team specifically and do not necessarily represent every stakeholder in the React Native community. We are sharing these principles here to be more transparent about what drives us, how we make decisions, and how we focus our efforts.

Native Experience

Our top priority for React Native is to match the expectations people have for each platform. This is why React Native renders to platform primitives. We value native look-and-feel over cross-platform consistency.

For example, the TextInput in React Native renders to a UITextField on iOS. This ensures that integration with password managers and keyboard controls work out of the box. By using platform primitives, React Native apps are also able to stay up-to-date with design and behavior changes from new releases of Android and iOS.

In order to match the look-and-feel of native apps, we must also match their performance. This is where we focus our most ambitious efforts. For example, Facebook created Hermes, a new JavaScript Engine built from scratch for React Native on Android. Hermes significantly improves the start time of React Native apps. We are also working on major architectural changes that optimize the threading model and make React Native easier to interoperate with native code.

Massive Scale

Hundreds of screens in the Facebook app are implemented with React Native. The Facebook app is used by billions of people on a huge range of devices. This is why we invest in the most challenging problems at scale.

Deploying React Native in our apps lets us identify problems that we wouldn’t see at a smaller scale. For example, Facebook focuses on improving performance across a broad spectrum of devices from the newest iPhone to many older generations of Android devices. This focus informs our architecture projects such as Hermes, Fabric, and TurboModules.

We have proven that React Native can scale to massive organizations too. When hundreds of developers are working on the same app, gradual adoption is a must. This is why we made sure that React Native can be adopted one screen at a time. Soon, we will be taking this one step further and enable migrating individual native views of an existing native screen to React Native.

A focus on massive scale means there are many things our team isn’t currently working on. For example, our team doesn’t drive the adoption of React Native in the industry. We also do not actively build solutions for problems that we don’t see at scale. We are proud that we have many partners and core contributors that are able to focus on those important areas for the community.

Developer Velocity

Great user experiences are created iteratively. It should only take a few seconds to seeing the result of code changes in a running app. React Native's architecture enables it to provide near-instant feedback during development.

We often hear from teams that adopting React Native significantly improved their development velocity. These teams find that the instant feedback during development makes it much easier to try different ideas and add extra polish when they don’t have to interrupt their coding session for every little change. When we make changes to React Native, we make sure to preserve this quality of the developer experience.

Instant feedback is not the only way that React Native improves developer velocity. Teams can easily leverage the fast-growing ecosystem of high quality open source packages. Teams can also share business logic between Android, iOS, and the web. This helps them ship updates faster and reduce organizational silos between platform teams.

Every Platform

When we introduced React Native in 2014, we presented it with our motto “Learn once, write anywhere” — and we mean anywhere. Developers should be able to reach as many people as possible without being limited by device model or operating system.

React Native targets very different platforms including mobile, desktop, web, TV, VR, game consoles, and more. We want to enable rich experiences on each platform instead of requiring developers to build for the lowest common denominator. To accomplish this, we focus on supporting the unique features of each platform. This ranges from varying input mechanisms (e.g. touch, pen, mouse) to fundamentally different consumption experiences like 3D environments in VR.

This principle informed our decision to implement React Native’s new core architecture in cross-platform C++ to promote parity across platforms. We are also refining the public interface targeted at other platform maintainers like Microsoft with Windows and macOS. We strive to enable any platforms to support React Native.

Declarative UI

We don’t believe in deploying the exact same user interface on every platform, we believe in exposing each platform’s unique capabilities with the same declarative programming model. Our declarative programming model is React.

In our experience, the unidirectional data flow popularized by React makes applications easier to understand. We prefer to express a screen as a composition of declarative components rather than imperatively managed views. React’s success on the web and the direction of the new native Android and iOS frameworks show that the industry has also embraced declarative UI.

React popularized declarative user interfaces. However, there remain many unsolved problems that React is uniquely positioned to solve. React Native will continue to build on top of the innovations of React and remain at the forefront of the declarative user interface movement.

Announcing React Native 0.63 with LogBox

Mike Grabowski

Mike Grabowski

CTO and Co-Founder at Callstack

Today we’re releasing React Native 0.63 that ships with LogBox turned on by default.

LogBox

We’ve heard frequent feedback from the community that errors and warnings are difficult to debug in React Native. To address these issues we took a look at the entire error, warning, and log system in React Native and redesigned it from the ground up.

Screenshot of LogBox

LogBox is a completely redesigned redbox, yellowbox, and logging experience in React Native. In 0.62 we introduced LogBox as an opt-in. In this release, we’re launching LogBox as the default experience in all of React Native.

LogBox addresses complaints that errors and warnings were too verbose, poorly formatted, or unactionable by focusing on three primary goals:

  • Concise: Logs should provide the minimum amount of information necessary to debug an issue.
  • Formatted: Logs should be formatted so that you can quickly find the information you need.
  • Actionable: Logs should be actionable, so you can fix the issue and move on.

To achieve these goals, LogBox includes:

  • Log notifications: We’ve redesigned the warning notifications and added support for errors so that all console.warn and console.log messages show up as notifications instead of covering your app.
  • Code Frames: Every error and warning now includes a code frame that shows the source code of the log right inside the app, allowing you to quickly identify the source of your issue.
  • Component Stacks: All component stacks are now stripped from error messages and put into their own section with the top three frames visible. This gives you a single, consistent space to expect stack frame information that doesn’t clutter the log message.
  • Stack Frame Collapsing: By default we now collapse call stack frames not related to your application’s code so you can quickly see the issue in your app and not sift through React Native internals.
  • Syntax Error Formatting: We’ve improved the formatting for syntax errors and added codeframes with syntax highlighting so you can see the source of the error, fix it, and continue coding without React Native getting in your way.

We’ve wrapped all of these features into an improved visual design that’s consistent between errors and warnings and allows paginating through all logs in one enjoyable UI.

With this change we’re also deprecating YellowBox in favor of LogBox APIs:

  • LogBox.ignoreLogs(): This function replaces YellowBox.ignoreLogs([]) as a way to silence any logs that match the given strings or regexes.
  • LogBox.ignoreAllLogs(): This function replaces console.disableYellowBox as a way to turn off error or warning notifications. Note: this only disables notifications, uncaught errors will still open a full screen LogBox.

In 0.63, we will warn when using these deprecated modules or methods. Please update your call sites off of these APIs before they are removed in 0.64.

For more information on LogBox and debugging react native, see the docs here.

Pressable

React Native is built to enable applications to meet user’s expectations of the platform. This includes avoiding “tells”—little things that give away that the experience was built with React Native. One major source of these tells has been the Touchable components: Button, TouchableWithoutFeedback, TouchableHighlight, TouchableOpacity, TouchableNativeFeedback, and TouchableBounce. These components make your application interactive by allowing you to provide visual feedback to user interactions. However, because they include built-in styles and effects that don’t match the platform interaction, users can tell when experiences are written with React Native.

Further, as React Native has grown and our bar for high-quality applications has gone up, these components haven't grown with it. React Native now supports platforms like Web, Desktop, and TV, but support for additional input modalities has been lacking. React Native needs to support high-quality interaction experiences on all platforms.

To address these problems, we are shipping a new core component called Pressable. This component can be used to detect various types of interactions. The API was designed to provide direct access to the current state of interaction without having to maintain state manually in a parent component. It was also designed to enable platforms to extend it's capabilities to include hover, blur, focus, and more. We expect that most people will build and share components utilizing Pressable under the hood instead of relying on the default experience of something like TouchableOpacity.

import { Pressable, Text } from 'react-native';
<Pressable
onPress={() => {
console.log('pressed');
}}
style={({ pressed }) => ({
backgroundColor: pressed ? 'lightskyblue' : 'white'
})}>
<Text style={styles.text}>Press Me!</Text>
</Pressable>;

A simple example of a Pressable component in action

You can learn more about it from the documentation.

Native Colors (PlatformColor, DynamicColorIOS)

Every native platform has the concept of system-defined colors. Colors that automatically respond to system theme settings such as Light or Dark mode, accessibility settings such as a High Contrast mode, and even its context within the app such as the traits of a containing view or window.

While it is possible to detect some of these settings via the Appearance API and/or AccessibilityInfo and set your styles accordingly, such abstractions are not only costly to develop but are just approximating the appearance of native colors. These inconsistencies are particularly noticeable when working on a hybrid application, where React Native elements co-exist next to the native ones.

React Native now provides an out-of-the-box solution to use these system colors. PlatformColor() is a new API that can be used like any other color in React Native.

For example, on iOS, the system provides a color called labelColor. That can be used in React Native with PlatformColor like this:

import { Text, PlatformColor } from 'react-native';
<Text style={{ color: PlatformColor('labelColor') }}>
This is a label
</Text>;

Sets the color of the Text component to labelColor as defined by iOS.

Android, on the other hand, provides colors like colorButtonNormal. You can use this color in React Native with:

import { View, Text, PlatformColor } from 'react-native';
<View
style={{
backgroundColor: PlatformColor('?attr/colorButtonNormal')
}}>
<Text>This is colored like a button!</Text>
</View>;

Sets the background color of the View component to colorButtonNormal as defined by Android.

You can learn more about PlatformColor from the documentation. You can also check the actual code examples present in the RNTester.

DynamicColorIOS is an iOS only API that lets you define which color to use in light and dark mode. Similar to PlatformColor, this can be used anywhere you can use colors. DynamicColorIOS uses iOS’s colorWithDynamicProvider under the hood.

import { Text, DynamicColorIOS } from 'react-native';
const customDynamicTextColor = DynamicColorIOS({
dark: 'lightskyblue',
light: 'midnightblue'
});
<Text style={{ color: customDynamicTextColor }}>
This color changes automatically based on the system theme!
</Text>;

Changes the text color based on the system theme

You can learn more about DynamicColorIOS from the documentation.

Dropping iOS 9 and Node.js 8 support

After over four years from its release, we are dropping support for iOS 9. This change will allow us to move faster by being able to reduce the number of compatibility checks that need to be placed in the native code to detect whether a given feature was supported on a certain iOS version. With its market share of 1%, it shouldn’t have much negative impact on your customers.

At the same time, we are dropping support for Node 8. Its LTS maintenance cycle expired in December 2019. The current LTS is Node 10 and it is now the version that we are targeting. If you are still using Node 8 for the development of React Native applications, we encourage you to upgrade in order to receive all the latest security fixes and updates.

Other notable improvements

  • Support rendering <View /> in <Text /> without explicit size: You can now render any <View /> inside any <Text /> component without setting its width and height explicitly, which wasn’t always possible. On previous releases of React Native, this would result in a RedBox.
  • Changed iOS LaunchScreen from xib to storyboard: Starting April 30, 2020, all apps submitted to the App Store must use an Xcode storyboard to provide the app’s launch screen and all iPhone apps must support all iPhone screens. This commit adjusts the default React Native template to be compatible with this requirement.

Thanks

Thank you to the hundreds of contributors that helped make 0.63 possible!

Special thanks to Rick Hanlon for authoring the section on LogBox and Eli White for authoring the Pressable part of this article.

To see all the updates, take a look at the 0.63 changelog.

Announcing React Native 0.62 with Flipper

Rick Hanlon

Rick Hanlon

React Native Core at Facebook

Today we’re releasing React Native version 0.62 which includes support for Flipper by default.

This release comes in the midst of a global pandemic. We’re releasing this version today to respect the work of hundreds of contributors who made this release possible and to prevent the release from falling too far behind master. Please be mindful of the reduced capacity of contributors to help with issues and prepare to delay upgrading if necessary.

Flipper by default

Flipper is a developer tool for debugging mobile apps. It’s popular in the Android and iOS communities, and in this release we’ve enabled support by default for new and existing React Native apps.

Screenshot of Flipper for React Native

Flipper provides the following features out of the box:

  • Metro Actions: Reload the app and trigger the Dev Menu right from the toolbar.
  • Crash Reporter: View crash reports from Android and iOS devices.
  • React DevTools: Use the newest version of React DevTools right alongside all your other tools.
  • Network Inspector: View all of the network requests made by device applications.
  • Metro and Device Logs: View, search, and filter all logs from both Metro and the Device.
  • Native Layout Inspector: View and edit the native layout output by the React Native renderer.
  • Database and Preference Inspectors: View and edit the device databases and preferences.

Additionally, since Flipper is an extensible platform, it provides a marketplace that pulls plugins from NPM so you can publish and install custom plugins specific to your workflows. See the available plugins here.

For more information, check out the Flipper documentation.

New dark mode features

We’ve added a new Appearance module to provide access to the user's appearance preferences, such as their preferred color scheme (light or dark).

const colorScheme = Appearance.getColorScheme();
if (colorScheme === 'dark') {
// Use dark color scheme
}

We’ve also added a hook to subscribe to state updates to the users preferences:

import { Text, useColorScheme } from 'react-native';
const MyComponent = () => {
const colorScheme = useColorScheme();
return <Text>useColorScheme(): {colorScheme}</Text>;
};

See the docs for Appearance and useColorScheme for more information.

Moving Apple TV to react-native-tvos

As part of our Lean Core effort and to bring Apple TV in line with other platforms like React Native Windows and React Native macOS, we’ve started to remove Apple TV specific code from core.

Going forward, Apple TV support for React Native will be maintained in react-native-community/react-native-tvos along with the corresponding react-native-tvos NPM package. This is a full fork of the main repository, with only the changes needed to support Apple TV.

Releases of react-native-tvos will be based on the public release of React Native. For this 0.62 release of react-native please upgrade Apple TV projects to use react-native-tvos 0.62.

More upgrade support

When 0.61 was released, the community introduced a new upgrade helper tool to support developers upgrading to new versions of React Native. The upgrade helper provides a diff of changes from the version you're on to the version you're targeting, allowing you to see the changes that need to be made for your specific upgrade.

Even with this tool, issues come up when upgrading. Today we're introducing more dedicated upgrading support by announcing Upgrade-Support. Upgrade Support is a GitHub issue tracker where users can submit issues specific to upgrading their projects to receive help from the community.

We're always working to improve the upgrade experience, and we hope that these tools give users the support they need in the edge cases we haven't covered yet.

Other improvements

  • LogBox: We’re adding the new LogBox error and warning experience as an opt-in; to enable it, add require('react-native').unstable_enableLogBox() to your index.js file.
  • React DevTools v4: This change includes an upgrade to the latest React DevTools which offers significant performance gains, an improved navigation experience, and full support for React Hooks.
  • Accessibility improvements: We’ve made improvements to accessibility including adding accessibilityValue, missing props on Touchables, onSlidingComplete accessibility events, and changing the default role of Switch component from "button" to "switch".

Breaking changes

  • Remove PropTypes: We're removing propTypes from core components in order to reduce the app size impact of React Native core and to favor static type systems which check at compile time instead of runtime.
  • Remove accessibilityStates: We’ve removed the deprecated accessibilityStates property in favor of the new accessibilityState prop which is a more semantically rich way for components to describe information about their state to accessibility services.
  • TextInput changes: We removed onTextInput from TextInput as it’s uncommon, not W3C compliant, and difficult to implement in Fabric. We also removed the undocumented inputView prop, and selectionState.

Deprecations

  • AccessibilityInfo.fetch was already deprecated, but in this release we added a warning.
  • Setting useNativeDriver is now required to support switching the default in the future.
  • The ref of an Animated component is now the internal component and deprecated getNode.

Thanks

Thank you to the hundreds of contributors that helped make 0.62 possible!

To see all the updates, take a look at the 0.62 changelog.

Meet Doctor, a new React Native command

Lucas Bento

Lucas Bento

React Native Community

After over 20 pull requests from 6 contributors in the React Native Community, we're excited to launch react-native doctor, a new command to help you out with getting started, troubleshooting and automatically fixing errors with your development environment. The doctor command is heavily inspired by Expo and Homebrew's own doctor command with a pinch of UI inspired by Jest.

Announcing React Native 0.61 with Fast Refresh

Dan Abramov

Dan Abramov

React Core at Facebook

We’re excited to announce React Native 0.61, which includes a new reloading experience we’re calling Fast Refresh.

Fast Refresh

When we asked the React Native community about common pain points, one of the top answers was that the “hot reloading” feature was broken. It didn’t work reliably for function components, often failed to update the screen, and wasn’t resilient to typos and mistakes. We heard that most people turned it off because it was too unreliable.

In React Native 0.61, we’re unifying the existing “live reloading” (reload on save) and “hot reloading” features into a single new feature called “Fast Refresh”. Fast Refresh was implemented from scratch with the following principles:

  • Fast Refresh fully supports modern React, including function components and Hooks.
  • Fast Refresh gracefully recovers after typos and other mistakes, and falls back to a full reload when needed.
  • Fast Refresh doesn’t perform invasive code transformations so it’s reliable enough to be on by default.

To see Fast Refresh in action, check out this video:

Give it a try, and let us know what you think! If you prefer, you can turn it off in the Dev Menu (Cmd+D on iOS, Cmd+M or Ctrl+M on Android). Turning it on and off is instant so you can do it any time.

Here are a few Fast Refresh tips:

  • Fast Refresh preserves React local state in function components (and Hooks!) by default.
  • If you need to reset the React state on every edit, you can add a special // @refresh reset comment to the file with that component.
  • Fast Refresh always remounts class components without preserving state. This ensures it works reliably.
  • We all make mistakes in the code! Fast Refresh automatically retries rendering after you save a file. You don't need to reload the app manually after fixing a syntax or a runtime error.
  • Adding a console.log or a debugger statement during edits is a neat debugging technique.

Please report any issues with Fast Refresh on GitHub, and we’ll look into them.

Other Improvements

  • Fixed use_frameworks! CocoaPods support. In 0.60 we made some updates to integrate CocoaPods by default. Unfortunately, this broke builds using use_frameworks!. This is fixed in 0.61, making it easier to integrate React Native into your iOS projects that require building with dynamic frameworks.
  • Add useWindowDimensions Hook. This new Hook automatically provides and subscribes to dimension updates, and can be used instead of the Dimensions API in most cases.
  • React was upgraded to 16.9. This version deprecates old names for the UNSAFE_ lifecycle methods, contains improvements to act, and more. See the React 16.9 blog post for an automated migration script and more information.

Breaking Changes

  • Remove React .xcodeproj. In 0.60, we introduced auto-linking support via CocoaPods. We have also integrated CocoaPods into the e2e tests runs, so that from now on, we have a unified standard way of integrating RN into iOS apps. This effectively deprecates the React .xcodeproj support, and the file has been removed starting 0.61. Note: if you use 0.60 auto-linking already, you shouldn't be affected.

Thanks

Thanks to all of the contributors that helped make 0.61 possible!

To see all the updates, take a look at the 0.61 changelog.

Meet Hermes, a new JavaScript Engine optimized for React Native

Rachel Nabors

Rachel Nabors

Documentation Engineer at Facebook

Last week at Chain React we announced Hermes, an open source JavaScript engine we’ve been working on at Facebook. It’s a small and lightweight JavaScript engine optimized for running React Native on Android. Check it out!

Hermes improves React Native performance by decreasing memory utilization, reducing download size, and decreasing the time it takes for the app to become usable or “time to interactive” (TTI).

“As we analyzed performance data, we noticed that the JavaScript engine itself was a significant factor in startup performance and download size. With this data in hand, we knew we had to optimize JavaScript performance in the more constrained environments of a mobile phone compared with a desktop or laptop. After exploring other options, we built a new JavaScript engine we call Hermes. It is designed to improve app performance, focusing on our React Native apps, even on mass-market devices with limited memory, slow storage, and reduced computing power.” —Hermes: An open source JavaScript engine optimized for mobile apps, starting with React Native

Want to get started right away? Be sure to check out our new guide to enabling Hermes in your existing React Native app in the docs!

Illustration of the Hermes and React Native logos joined into a winged fury, rising in a crashing electrical storm from a lone, glowing, presumably Android phone. Illustration by Rachel Nabors

Announcing React Native 0.60

Ryan Turner

Ryan Turner

Core Maintainer & React Native Developer

After months of hard work from hundreds of contributors, the React Native Core team is proud to announce the release of version 0.60. This release handles significant migrations for both Android and iOS platforms, and many issues are resolved too. This blog post covers the highlights of the release. As always though, refer to the changelog for more detailed information. Finally, thank you contributors for helping us to make this milestone!

Focus on Accessibility

There have been many improvements to the accessibility APIs, like announceForAccessibility, plus improvements to roles, action support, flags, and more. Accessibility is a complex science, but we hope these improvements make it a bit easier to be an A11Y. Be sure to check React Native Open Source Update June 2019 for more details of these changes.

A Fresh Start

React Native's start screen has been updated! Thank you to the many contributors who helped create the new UI. This new "Hello World" will welcome users to the ecosystem in a more friendly, engaging way.

The new init screen helps developers get started from the get-go with resources and a good example

AndroidX Support

AndroidX is a major step forward in the Android ecosystem, and the old support library artifacts are being deprecated. For 0.60, React Native has been migrated over to AndroidX. This is a breaking change, and your native code and dependencies will need to be migrated as well.

With this change, React Native apps will need to begin using AndroidX themselves. They cannot be used side-by-side in one app, so all of the app code and dependency code needs to be using one or the other.

matt-oakes on discussions-and-proposals

While your own native code will need to be migrated by you, @mikehardy, @cawfree, and @m4tt72 built a clever tool named "jetifier" to patch your node_modules. Library maintainers will need to upgrade, but this tool provide you with a temporary solution while giving them time to release an AndroidX version. So if you find errors related to AndroidX migration, give this a shot.

CocoaPods by Default

CocoaPods are now part of React Native's iOS project. If you weren't already, be sure to open iOS platform code using the xcworkspace file from now on (protip: try xed ios from the root project directory). Also, the podspecs for the internal packages have changed to make them compatible with the Xcode projects, which will help with troubleshooting and debugging. Expect to make some straightforward changes to your Podfile as part of the upgrade to 0.60 to bring this exciting support. Note that we are aware of a compatibility issue with use_frameworks!, and we're tracking an issue with workarounds and a future patch.

Lean Core Removals

WebView and NetInfo were previously extracted into separate repositories, and in 0.60 we’ve finished migrating them out of the React Native repository. Additionally, in response to community feedback about new App Store policy, Geolocation has been extracted. If you haven’t already, complete your migration by adding dependencies to react-native-webview, @react-native-community/netinfo, and @react-native-community/geolocation. If you'd like an automated solution, consider using rn-upgrade-deprecated-modules. Maintainers have made more than 100 commits to these repositories since extraction and we’re excited to see the community’s support!

Native Modules are now Autolinked

The team working on the React Native CLI has introduced major improvements to native module linking called autolinking! Most scenarios will not require the use of react-native link anymore. At the same time, the team overhauled the linking process in general. Be sure to react-native unlink any preexisting dependencies as mentioned in the docs above.

Upgrade Helper

@lucasbento, @pvinis, @kelset, and @watadarkstar have built a great tool called Upgrade Helper to make the upgrade process simpler. It helps React Native users with brownfield apps or complex customizations to see what's changed between versions. Take a look at the updated upgrading docs and try it out today for your upgrade path!

Upgrade Helper cleanly and easily shows the changes needed to migrate to a different version of React Native

A Note to Library Maintainers

Changes for AndroidX will almost certainly require updates to your library, so be sure to include support soon. If you're not able to upgrade yet, consider checking your library against the jetifier to confirm that users are able to patch your library at build time.

Review the autolinking docs to update your configs and readme. Depending on how your library was previously integrated, you may also need to make some additional changes. Check the dependencies guide from the CLI for information on how to define your dependency interface.

Thanks

While these are the highlights that we noted, there are many others to be excited about. To see all the updates, take a look at the changelog. As always, stay tuned for more news. Enjoy 0.60 in the meantime!

React Native Open Source Update June 2019

Christoph Nakazawa

Christoph Nakazawa

Engineer at Facebook

Code & Community Health

In the past six months, a total of 2800 commits were made to React Native by more than 550 contributors. 400 contributors from the community created more than 1,150 Pull Requests, of which 820 Pull Requests were merged.

The average number of Pull Requests per day throughout the past six months has increased from three to about six, even though we split the website, CLI and many modules out of React Native via the Lean Core effort. The average amount of open pull requests is now below 25 and we usually reply with suggestions and reviews within hours or days.

Meaningful Community Contributions

We’d like to highlight a number of recent contributions which we thought were awesome:

Lean Core

The primary motivation of Lean Core has been to split modules out of React Native into separate repositories so they can receive better maintenance. In just a six months repositories like WebView, NetInfo, AsyncStorage, the website and the CLI received more than 800 Pull Requests combined. Besides better maintenance, these projects can also be independently released more often than React Native itself.

We have also taken the opportunity to remove obsolete polyfills and legacy components from React Native itself. Polyfills were necessary in the past to support language features like Map and Set in older versions of JavaScriptCore (JSC). Now that React Native ships with a new version, these polyfills were removed.

This work is still in progress and many more things still need to be split out or removed both on the native and JavaScript side but there are early signs that we managed to reverse the trend of increasing the surface area and app size: When looking at the JavaScript bundle for example, about a year ago in version 0.54 the React Native JavaScript bundle size was 530kb and grew to 607kb (+77kb) by version 0.57 in just 6 months. Now we are seeing a bundle size reduction of 28kb down to 579kb on master, a delta of more than 100kb!

As we conclude the first iteration of the Lean Core effort, we will make an effort to be more intentional about new APIs added to React Native and we will continuously evaluate ways to make React Native smaller and faster, as well as finding ways to empower the community to take ownership of various components.

User Feedback

Six months ago we asked the community “What do you dislike about React Native?” which gave a good overview of problems people are facing. We replied to the post a few months ago and it's time to summarize the progress that was made on top issues:

  • Upgrading: The React Native community rallied around with multiple improvements to the upgrading experience: autolinking, a better upgrading command via rn-diff-purge, an upgrade helper website (coming soon). We’ll also make sure to communicate breaking changes and exciting new features by publishing blog posts for each major release. Many of these improvements will make future upgrades beyond the 0.60 release significantly easier.
  • Support / Uncertainty: Many people were frustrated with the lack of activity on Pull Requests and general uncertainty about Facebook's investment in React Native. As we've shown above, we can confidently say that we are ready for many more Pull Requests and we are eagerly looking forward to your proposals and contributions!
  • Performance: React Native 0.59 shipped with a new and much faster version of JavaScriptCore (JSC). Separately, we have been working on making it easier to enable inline-requires by default and we have more exciting updates for you in the next couple of months.
  • Documentation: We recently started an effort to overhaul and rewrite all of React Native's documentation. If you are looking to contribute, we’d love to get your help!
  • Warnings in Xcode: We got rid of all the existing warnings and are making an effort not to introduce new warnings.
  • Hot Reloading: The React team is building a new hot reloading system that will soon be integrated into React Native.

Unfortunately we weren’t able to improve everything just yet:

  • Debugging: We fixed many inconvenient bugs and issues people that we have been running into every day, but unfortunately we haven't made as much progress on this as we would like. We recognize that debugging with React Native isn't great and we'll prioritize improving this in the future.
  • Metro symlinks: Unfortunately we haven't been able to implement a simple and straightforward solution for this yet. However, React Native users shared various workarounds that may work for you.

Given the large amount of changes in the past six months, we'd like to ask you the same question again. If you are using the latest version of React Native and you have things you'd like to give feedback on, please comment on our new edition of “What do you dislike about React Native?”

Continuous Integration

Facebook merges all Pull Requests and internal changes directly into Facebook’s repository first and then syncs all commits back to GitHub. Facebook’s infrastructure is different from common continuous integration services and not all open source tests were run inside of Facebook. This means that commits that sync out to GitHub frequently break tests in open source which take a lot of time to fix.

Héctor Ramos from the React Native team spent the past two months improving React Native's continuous integration systems both at Facebook and on GitHub. Most of the open source tests are now run before changes are committed to React Native at Facebook which will keep CI stable on GitHub when commits are being synchronized.

Next

Make sure to check out our talks about the future of React Native! In the next couple of months, members of the React Native team at Facebook will speak at Chain React and at React Native EU. Also, watch out for our next release, 0.60, which is right around the corner. It's going to be exciting

React Native at F8 and Open Source Podcast

Christoph Nakazawa

Christoph Nakazawa

Engineer at Facebook

This week, Eli White gave a talk at F8 2019 about React Native in Facebook's Android and iOS applications. We are excited to share what we've been up to for the past two years and what we're doing next.

Check out the video on Facebook's developer website:

F8 Talk about React Native

Highlights from the talk:

  • We spent 2017 and 2018 focused on React Native's largest product, Facebook's Marketplace. We collaborated with the Marketplace team to improve quality and add delight to the product. At this point, Marketplace is one of the highest quality products in the Facebook app both on Android and iOS.
  • Marketplace's performance was a big challenge as well, especially on mid-end Android devices. We cut startup time by more than 50% over the last year with more improvements on the way! The biggest improvements are being built into React Native and will be coming to the community later this year.
  • We have the confidence that we can build the high quality and performant apps that Facebook needs with React Native. This confidence has let us invest in bigger bets, like rethinking the core of React Native.
  • Microsoft supports and uses React Native for Windows, enabling people to use their expertise and codebase to render to Microsofts's Universal Windows Platform. Check out Microsoft Build next week to hear them talk about that more.

React Radio Podcast about Open Source

Eli's talk concludes by talking about our recent open source work. We gave an update on our progress in March and recently Nader Dabit and Gant Laborde invited Christoph for a chat on their podcast, React Native Radio, to chat about React Native in open source.

Highlights from the podcast:

  • We talked about how the React Native team at Facebook thinks about open source and how we are building a sustainable community that scales for a project of React Native's size.
  • We are on track to remove multiple modules as part of the Lean Core effort. Many modules like WebView and the React Native CLI have received more than 100 Pull Requests since they were extracted.
  • Next, we'll be focusing on overhauling the React Native website and documentation. Stay tuned!

You'll find the episode in your favorite podcasting app soon or you can listen to the recording right here:

Releasing React Native 0.59

Ryan Turner

Ryan Turner

Core Maintainer & React Native Developer

Welcome to the 0.59 release of React Native! This is another big release with 644 commits by 88 contributors. Contributions also come in other forms, so thank you for maintaining issues, fostering communities, and teaching people about React Native. This month brings a number of highly anticipated changes, and we hope you enjoy them.

🎣 Hooks are here

React Hooks are part of this release, which let you reuse stateful logic across components. There is a lot of buzz about hooks, but if you haven't heard, take a look at some of the wonderful resources below:

Be sure to give this a try in your apps. We hope that you find the reuse as exciting as we do.

📱 Updated JSC means performance gains and 64-bit support on Android

React Native uses JSC (JavaScriptCore) to power your application. JSC on Android was a few years old, which meant that a lot of modern JavaScript features weren't supported. Even worse, it performed poorly compared iOS's modern JSC. With this release, that all changes.

Thanks to some awesome work by @DanielZlotin, @dulmandakh, @gengjiawen, @kmagiera, and @kudo JSC has caught up with the past few years. This brings with it 64-bit support, modern JavaScript support, and big performance improvements. Kudos for also making this a maintainable process now so that we can take advantage of future WebKit improvements without so much legwork, and thank you Software Mansion and Expo for making this work possible.

💨 Faster app launches with inline requires

We want to help people have performant React Native apps by default and are working to bring Facebook's optimizations to the community. Applications load resources as needed rather than slowing down launch. This feature is called "inline requires", as it lets Metro identify components to be lazy loaded. Apps with a deep and varied component architecture will see the most improvement.

source of the `metro.config.js` file in the 0.59 template, demonstrating where to enable `inlineRequires`

We need the community to let us know how it works before we turn it on by default. When you upgrade to 0.59, there will be a new metro.config.js file; flip the options to true and give us your feedback! Read more about inline requires in the performance docs to benchmark your app.

🚅 Lean core is underway

React Native is a large and complex project with a complicated repository. This makes the codebase less approachable to contributors, difficult to test, and bloated as a dev dependency. Lean Core is our effort to address these issues by migrating code to separate libraries for better management. The past few releases have seen the first steps of this, but let's get serious.

You may notice that additional components are now officially deprecated. This is great news, as there are now owners for these features actively maintaining them. Heed the warning messages and migrate to the new libraries for these features, because they will be removed in a future release. Below is a table indicating the component, its status, and where you may migrate your use to.

ComponentDeprecated?New home
AsyncStorage0.59@react-native-community/react-native-async-storage
ImageStore0.59expo-file-system or react-native-fs
MaskedViewIOS0.59@react-native-community/react-native-masked-view
NetInfo0.59@react-native-community/react-native-netinfo
Slider0.59@react-native-community/react-native-slider
ViewPagerAndroid0.59@react-native-community/react-native-viewpager

Over the coming months, there will be many more components following this path to a leaner core. We're looking for help with this — head over to the lean core umbrella to pitch in.

👩🏽‍💻 CLI improvements

React Native's command line tools are developer's entry point to the ecosystem, but they had long-standing issues and lacked official support. The CLI tools have been moved to a new repository, and a dedicated group of maintainers have already made some exciting improvements.

Logs are formatted much better now. Commands now run nearly instantly — you'll immediately notice a difference:

0.58's CLI is slow to start0.58's CLI is nearly instantaneous

🚀 Upgrading to 0.59

We heard your feedback regarding the React Native upgrade process and we are taking steps to improve the experience in future releases. To upgrade to 0.59, we recommend using rn-diff-purge to determine what has changed between your current React Native version and 0.59, then applying those changes manually. Once you've upgraded your project to 0.59, you will be able to use the newly improved react-native upgrade command (based on rn-diff-purge!) to upgrade to 0.60 and beyond as newer releases become available.

🔨 Breaking Changes

Android support in 0.59 has been cleaned up following Google's latest recommendations, which may result in potential breakage of existing apps. This issue might present as a runtime crash and a message, "You need to use a Theme.AppCompat theme (or descendant) with this activity". We recommend updating your project's AndroidManifest.xml file, making sure that the android:theme value is an AppCompat theme (such as @style/Theme.AppCompat.Light.NoActionBar).

The react-native-git-upgrade command has been removed in 0.59, in favor of the newly improved react-native upgrade command.

🤗 Thanks

Lots of new contributors helped with enabling generation of native code from flow types and resolving Xcode warnings - these are a great way to learn how React Native works and contributing to the greater good. Thank you! Look out for similar issues in the future.

While these are the highlights that we noted, there are many others to be excited about. To see all of the updates, take a look at the changelog. 0.59 is a huge release – we can't wait for you to try it out.

We have even more improvements coming throughout the rest of the year. Stay tuned!

Ryan and the whole React Native core team

React Native Open Source Update March 2019

Christoph Nakazawa

Christoph Nakazawa

Engineer at Facebook

We announced our React Native Open Source roadmap in Q4 2018 after deciding to invest more in the React Native open source community.

For our first milestone, we focused on identifying and improving the most visible aspects of our community. Our goals were to reduce outstanding pull requests, reduce the project's surface area, identify leading user problems, and establish guidelines for community management.

In the past two months, we made more progress than we expected. Read on for more details:

Pull Requests

In order to build a healthy community, we must respond quickly to code contributions. In past years, we de-prioritized reviewing community contributions and accumulated 280 pull requests (December 2018). In the first milestone, we reduced the number of open pull requests to ~65. Simultaneously, the average number of pull requests opened per day increased from 3.5 to 7 which means we have handled about 600 pull requests in the last three months.

We merged almost two-thirds and closed one-third of the pull requests. They were closed without being merged if they are obsolete or low quality, or if they unnecessarily increase the project's surface area. Most of the merged pull requests fixed bugs, improved cross-platform parity, or introduced new features. Notable contributions include improving type safety and the ongoing work to support AndroidX.

At Facebook, we run React Native from master, so we test all changes first before they make it into a React Native Release. Out of all the merged pull requests, only six caused issues: four only affected internal development and two were caught in the release candidate state.

One of the more visible community contributions was the updated “RedBox” screen. It's a good example of how the community is making the developer experience friendlier.

Lean Core

React Native currently has a very wide surface area with many unmaintained abstractions that we do not use a lot at Facebook. We are working on reducing the surface area in order to make React Native smaller and allow the community to take better care of abstractions that are mostly unused at Facebook.

In the first milestone, we asked the community for help on the Lean Core project. The response was overwhelming and we could barely keep up with all the progress. Check out all the work completed in less than a month!

What we are most excited about is that maintainers have jumped in fixing long standing issues, adding tests, and supporting long requested features. These modules are getting more support than they ever did within React Native, showing that this is a great step for the community. Examples of such projects are WebView that has received many pull requests since their extraction and the CLI that is now maintained by members of the community and received much needed improvements and fixes.

Leading User Problems

In December, we asked the community what they disliked about React Native. We aggregated the responses and replied to each and every problem. Fortunately, many of the issues that our community faces are also problems at Facebook. In our next milestone, we plan to address some of the main problems.

One of the highest voted problems was the developer experience of upgrading to newer versions of React Native. Unfortunately, this is not something that we experience ourselves because we run React Native from master. Thankfully, members from the community already stepped up to address this problem:

0.59 Release

Without the help of the React Native community, especially Mike Grabowski and Lorenzo Sciandra, we would not be able to ship releases. We want to improve the release management process and plan to be more involved from now on:

  • We will work with community members to create a blog post for each major release.
  • We will show breaking changes directly in the CLI when people upgrade to new versions.
  • We will reduce the time it takes to make a release. We are exploring ways to increase automated testing and also creating an improved manual test plan.

Many of these plans will be incorporated in the upcoming React Native 0.59 release. 0.59 will ship with React Hooks, a new 64-bit version of JavaScriptCore for Android, and many performance and functionality improvements. It is currently published as a release candidate and is expected to be stable within the next two weeks.

Next Steps

For the next two months, we will continue managing pull requests to stay on track while also starting to reduce the number of outstanding GitHub issues. We will continue reducing the surface area of React Native through the Lean Core project. We plan to address 5 of the top community problems. As we finalize the community guidelines, we will turn attention to our website and documentation.

We are very excited to host over ten contributors from our community at Facebook London in March to help drive several of these efforts. We are glad that you are using React Native and hope that you'll see and feel the improvements we are working on in 2019. We'll be back with another update in a few months and will be merging your pull requests in the meantime! ⚛️✌️

The State of the React Native Community in 2018

Lorenzo Sciandra

Lorenzo Sciandra

Core Maintainer & React Native Developer

In 2018 the React Native Community made a number of changes to the way we develop and communicate about React Native. We believe that a few years from now we will look back and see that this shift was a turning point for React Native.

A lot of people are excited about the rewrite of React Native's architecture, widely known as Fabric. Among other things, this will fix fundamental limitations in React Native's architecture and will set up React Native for success in the future together with JSI and TurboModules.

The biggest shift in 2018 was to empower the React Native Community. From the beginning, Facebook encouraged developers from all around the world to participate in React Native's open source project. Since then, a number of core contributors emerged to handle, among other things, the release process.

These members took a few substantial steps towards making the whole community more empowered to shape the future of this project with the following resources:

react-native-releases 📬

This repository, created in January, serves the dual purpose of allowing everyone to keep up the new releases in a more collaborative manner and opened the conversation of what would be part of a certain release to whomever wanted to suggest a cherry-pick (like for 0.57.8 and all its previous versions).

This has been the driving force behind moving away from a monthly release cycle, and the "long term support" approach currently used for version 0.57.x.

Half of the credit for reaching these decisions goes to the other repository created this year:

discussions-and-proposals 🗣

This repository, created in July, expanded on the idea of a more open environment for conversations on React Native. Previously, this need was handled by issues labelled For Discussion in the main repository, but we wanted to expand this strategy to an RFC approach that other libraries have (e.g. React).

This experiment immediately found its role in the React Native lifecycle. The Facebook team is now using the community RFC process to discuss what could be improved in React Native, and coordinate the efforts around the Lean Core project - among other interesting discussions.

@ReactNativeComm 🐣

We are aware that our approach to communicate these efforts has not been as effective as we would have liked, and in an attempt to give you all an easier time keeping up with everything going on in the React Native Community (from releases to active discussions) we created a new twitter account that you can rely on @ReactNativeComm.

If you are not on that social network, remember that you can always watch repositories via GitHub; this feature improved these past few months with the possibility of being notified only for releases, so you should consider using it anyway.

What awaits ahead 🎓

Over the past 7-8 months, core contributors enhanced the React Native Community GitHub organization to take more ownership over the development of React Native, and enhance collaboration with Facebook. But this always lacked the formal structure that similar projects may have in place.

This organization can set the example for everyone in the larger developer community by enforcing a set of standards for all the packages/repos hosted in it, providing a single place for maintainers to help each other and contribute quality code that conforms to community-agreed standards.

In early 2019, we will have this new set of guidelines in place. Let us know what you think in the dedicated discussion.

We are confident that with these changes, the community will become more collaborative so that when we reach 1.0, we will all continue to write (even more) awesome apps by leveraging this joint effort 🤗


I hope you are as excited as we are about the future of this community. We're excited to see all of you involved either in the conversations happening in the repositories listed above or via the awesome code you’ll produce.

Happy coding!

Open Source Roadmap

Héctor Ramos

Héctor Ramos

Engineer at Facebook

This year, the React Native team has focused on a large scale re-architecture of React Native. As Sophie mentioned in her State of React Native post, we've sketched out a plan to better support the thriving population of React Native users and collaborators outside of Facebook. It's now time to share more details about what we've been working on. Before I do so, I'd like to lay out our long-term vision for React Native in open source.

Our vision for React Native is...

  • A healthy GitHub repository. Issues and pull requests get handled within a reasonable period of time.
    • Increased test coverage.
    • Commits that sync out from the Facebook code repository should not break open source tests.
    • A higher scale of meaningful community contributions.
  • Stable APIs, making it easier to interface with open source dependencies.
    • Facebook uses the same public API as open source
    • React Native releases that follow semantic versioning.
  • A vibrant eco-system. High quality ViewManagers, native modules, and multiple platform support maintained by the community.
  • Excellent documentation. Focus on helping users create high quality experiences, and up-to-date API reference docs.

We have identified the following focus areas to help us achieve this vision.

✂️ Lean Core

Our goal is to reduce the surface area of React Native by removing non-core and unused components. We'll transfer non-core components to the community to allow it to move faster. The reduced surface area will make it easier to manage contributions to React Native.

WebView is an example of a component that we transferred to the community. We are working on a workflow that will allow internal teams to continue using these components after we remove them from the repository. We have identified dozens more components that we'll give ownership of to the community.

🎁 Open Sourcing Internals and 🛠Updated Tooling

The React Native development experience for product teams at Facebook can be quite different from open source. Tools that may be popular in the open source community are not used at Facebook. There may be an internal tool that achieves the same purpose. In some cases, Facebook teams have become used to tools that do not exist outside of Facebook. These disparities can pose challenges when we open source our upcoming architecture work.

We'll work on releasing some of these internal tools. We'll also improve support for tools popular with the open source community. Here's a non-exhaustive list of projects we'll tackle:

  • Open source JSI and enable the community to bring their own JavaScript VMs, replacing the existing JavaScriptCore from RN's initial release. We'll be covering what JSI is in a future post, in the meantime you can learn more about JSI from Parashuram's talk at React Conf.
  • Support 64-bit libraries on Android.
  • Enable debugging under the new architecture.
  • Improve support for CocoaPods, Gradle, Maven, and new Xcode build system.

✅ Testing Infrastructure

When Facebook engineers publish code, it's considered safe to land if it passes all tests. These tests identify whether a change might break one of our own React Native surfaces. Yet, there are differences in how Facebook uses React Native. This has allowed us to unknowingly break React Native in open source.

We'll shore up our internal tests to ensure they run in an environment that is as close as possible to open source. This will help prevent code that breaks these tests from making it to open source. We will also work on infrastructure to enable better testing of the core repo on GitHub, enabling future pull requests to easily include tests.

Combined with the reduced surface area, this will allow contributors to merge pull requests quicker, with confidence.

📜 Public API

Facebook will consume React Native via the public API, the same way open source does, to reduce unintentional breaking changes. We have started converting internal call sites to address this. Our goal is to converge on a stable, public API, leading to the adoption of semantic versioning in version 1.0.

📣 Communication

React Native is one of the top open source projects on GitHub by contributor count. That makes us really happy, and we'd like to keep it going. We'll continue working on initiatives that lead to involved contributors, such as increased transparency and open discussion. The documentation is one of the first things someone new to React Native will encounter, yet it has not been a priority. We'd like to fix that, starting with bringing back auto-generated API reference docs, creating additional content focused on creating quality user experiences, and improving our release notes.

Timeline

We're planning to land these projects throughout the next year or so. Some of these efforts are already ongoing, such as JSI which has already landed in open source. Others will take a bit longer to complete, such as reducing the surface area. We'll do our best to keep the community up to date with our progress. Please join us in the Discussions and Proposals repository, a initiative from the React Native community that has led to the creation of several of the initiatives discussed in this roadmap.

Releasing 0.56

Lorenzo Sciandra

Lorenzo Sciandra

Core Maintainer & React Native Developer at Drivetribe

The long-awaited 0.56 version of React Native is now available 🎉. This blog post highlights some of the changes introduced in this new release. We also want to take the opportunity to explain what has kept us busy since March.

The breaking changes dilemma, or, "when to release?"

The Contributor's Guide explains the integration process that all changes to React Native go through. The project has is composed by many different tools, requiring coordination and constant support to keep everything working properly. Add to this the vibrant open source community that contributes back to the project, and you will get a sense of the mind-bending scale of it all.

With React Native's impressive adoption, breaking changes must be made with great care, and the process is not as smooth as we'd like. A decision was made to skip the April and May releases to allow the core team to integrate and test a new set of breaking changes. Dedicated community communication channels were used along the way to ensure that the June 2018 (0.56.0) release is as hassle-free as possible to adopt by those who patiently waited for the stable release.

Is 0.56.0 perfect? No, as every piece of software out there: but we reached a point where the tradeoff between "waiting for more stability" versus "testing led to successful results so we can push forward" that we feel ready to release it. Moreover, we are aware of a few issues that are not solved in the final 0.56.0 release. Most developers should have no issues upgrading to 0.56.0. For those that are blocked by the aforementioned issues, we hope to see you around in our discussions and we are looking forward to working with you on a solution to these issues.

You might consider 0.56.0 as a fundamental building block towards a more stable framework: it will take probably a week or two of widespread adoption before all the edge cases will be sanded off, but this will lead to an even better July 2018 (0.57.0) release.

We'd like to conclude this section by thanking all the 67 contributors who worked on a total of 818 commits (!) that will help make your apps even better 👏.

And now, without further ado...

The Big Changes

Babel 7

As you may know, the transpiler tool that allows us all to use the latest and greatest features of JavaScript, Babel, is moving to v7 soon. Since this new version brings along some important changes, we felt that now it would be a good time to upgrade, allowing Metro to leverage on its improvements.

If you find yourself in trouble with upgrading, please refer to the documentation section related to it.

Modernizing Android support

On Android, much of the surrounding tooling has changed. We've updated to Gradle 3.5, Android SDK 26, Fresco to 1.9.0, and OkHttp to 3.10.0 and even the NDK API target to API 16. These changes should go without issue and result in faster builds. More importantly, it will help developers comply with the new Play Store requirements coming into effect next month.

Related to this, we'd like to particularly thank Dulmandakh for the many PRs submitted in order to make it possible 👏.

There are some more steps that need to be taken in this direction, and you can follow along with the future planning and discussion of updating the Android support in the dedicated issue (and a side one for the JSC).

New Node, Xcode, React, and Flow – oh my!

Node 8 is now the standard for React Native. It was actually already being tested already, but we've put both feet forward as Node 6 entered maintenance mode. React was also updated to 16.4, which brings a ton of fixes with it.

We're dropping support for iOS 8, making iOS 9 the oldest iOS version that can be targeted. We do not foresee this being a problem, as any device that can run iOS 8, can be upgraded to iOS 9. This change allowed us to remove rarely-used code that implemented workarounds for older devices running iOS 8.

The continuous integration toolchain has been updated to use Xcode 9.4, ensuring that all iOS tests are run on the latest developer tools provided by Apple.

We have upgraded to Flow 0.75 to use the new error format that many devs appreciate. We've also created types for many more components. If you're not yet enforcing static typing in your project, please consider using Flow to identify problems as you code instead of at runtime.

And a lot of other things...

For instance, YellowBox was replaced with a new implementation that makes debugging a lot better.

For the complete release notes, please reference the full changelog here. And remember to keep an eye on the upgrading guide to avoid issues moving to this new version.


A final note: starting this week, the React Native core team will resume holding monthly meetings. We'll make sure to keep everyone up-to-date with what's covered, and ensure to keep your feedback at hand for future meetings.

Happy coding everyone!

Lorenzo, Ryan, and the whole React Native core team

PS: as always, we'd like to remind everyone that React Native is still in 0.x versioning because of the many changes still undergoing - so remember when upgrading that yes, probably, something may still crash or be broken. Be helpful towards each other in the issues and when submitting PRs - and remember to follow the CoC enforced: there's always a human on the other side of the screen.

A Monthly Release Cadence: Releasing December and January RC

Eric Vicenti

Eric Vicenti

Engineer at Facebook

Shortly after React Native was introduced, we started releasing every two weeks to help the community adopt new features, while keeping versions stable for production use. At Facebook we had to stabilize the codebase every two weeks for the release of our production iOS apps, so we decided to release the open source versions at the same pace. Now, many of the Facebook apps ship once per week, especially on Android. Because we ship from master weekly, we need to keep it quite stable. So the bi-weekly release cadence doesn't even benefit internal contributors anymore.

We frequently hear feedback from the community that the release rate is hard to keep up with. Tools like Expo had to skip every other release in order to manage the rapid change in version. So it seems clear that the bi-weekly releases did not serve the community well.

Now releasing monthly

We're happy to announce the new monthly release cadence, and the December 2016 release, v0.40, which has been stabilizing for all last month and is ready to adopt. (Just make sure to update headers in your native modules on iOS).

Although it may vary a few days to avoid weekends or handle unforeseen issues, you can now expect a given release to be available on the first day of the month, and released on the last.

Use the current month for the best support

The January release candidate is ready to try, and you can see what's new here.

To see what changes are coming and provide better feedback to React Native contributors, always use the current month's release candidate when possible. By the time each version is released at the end of the month, the changes it contains will have been shipped in production Facebook apps for over two weeks.

You can easily upgrade your app with the new react-native-git-upgrade command:

npm install -g react-native-git-upgrade
react-native-git-upgrade 0.41.0-rc.0

We hope this simpler approach will make it easier for the community to keep track of changes in React Native, and to adopt new versions as quickly as possible!

(Thanks go to Martin Konicek for coming up with this plan and Mike Grabowski for making it happen)

Easier Upgrades Thanks to Git

Nicolas Cuillery

Nicolas Cuillery

JavaScript consultant and trainer at Zenika

Upgrading to new versions of React Native has been difficult. You might have seen something like this before:

None of those options is ideal. By overwriting the file we lose our local changes. By not overwriting we don't get the latest updates.

Today I am proud to introduce a new tool that helps solve this problem. The tool is called react-native-git-upgrade and uses Git behind the scenes to resolve conflicts automatically whenever possible.

Usage

Requirement: Git has to be available in the PATH. Your project doesn't have to be managed by Git.

Install react-native-git-upgrade globally:

$ npm install -g react-native-git-upgrade

or, using Yarn:

$ yarn global add react-native-git-upgrade

Then, run it inside your project directory:

$ cd MyProject
$ react-native-git-upgrade 0.38.0

Note: Do not run 'npm install' to install a new version of react-native. The tool needs to be able to compare the old and new project template to work correctly. Simply run it inside your app folder as shown above, while still on the old version.

Example output:

You can also run react-native-git-upgrade with no arguments to upgrade to the latest version of React Native.

We try to preserve your changes in Android and iOS build files, so you don't need to run react-native link after an upgrade.

We have designed the implementation to be as little intrusive as possible. It is entirely based on a local Git repository created on-the-fly in a temporary directory. It won't interfere with your project repository (no matter what VCS you use: Git, SVN, Mercurial, ... or none). Your sources are restored in case of unexpected errors.

How does it work?

The key step is generating a Git patch. The patch contains all the changes made in the React Native templates between the version your app is using and the new version.

To obtain this patch, we need to generate an app from the templates embedded in the react-native package inside your node_modules directory (these are the same templates the react-native init commands uses). Then, after the native apps have been generated from the templates in both the current version and the new version, Git is able to produce a patch that is adapted to your project (i.e. containing your app name):

[...]
diff --git a/ios/MyAwesomeApp/Info.plist b/ios/MyAwesomeApp/Info.plist
index e98ebb0..2fb6a11 100644
--- a/ios/MyAwesomeApp/Info.plist
+++ b/ios/MyAwesomeApp/Info.plist
@@ -45,7 +45,7 @@
<dict>
<key>localhost</key>
<dict>
- <key>NSTemporaryExceptionAllowsInsecureHTTPLoads</key>
+ <key>NSExceptionAllowsInsecureHTTPLoads</key>
<true/>
</dict>
</dict>
[...]

All we need now is to apply this patch to your source files. While the old react-native upgrade process would have prompted you for any small difference, Git is able to merge most of the changes automatically using its 3-way merge algorithm and eventually leave us with familiar conflict delimiters:

13B07F951A680F5B00A75B9A /* Release */ = {
isa = XCBuildConfiguration;
buildSettings = {
ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
<<<<<<< ours
CODE_SIGN_IDENTITY = "iPhone Developer";
FRAMEWORK_SEARCH_PATHS = (
"$(inherited)",
"$(PROJECT_DIR)/HockeySDK.embeddedframework",
"$(PROJECT_DIR)/HockeySDK-iOS/HockeySDK.embeddedframework",
);
=======
CURRENT_PROJECT_VERSION = 1;
>>>>>>> theirs
HEADER_SEARCH_PATHS = (
"$(inherited)",
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include,
"$(SRCROOT)/../node_modules/react-native/React/**",
"$(SRCROOT)/../node_modules/react-native-code-push/ios/CodePush/**",
);

These conflicts are generally easy to reason about. The delimiter ours stands for "your team" whereas theirs could be seen as "the React Native team".

Why introduce a new global package?

React Native comes with a global CLI (the react-native-cli package) which delegates commands to the local CLI embedded in the node_modules/react-native/local-cli directory.

As we mentioned above, the process has to be started from your current React Native version. If we had embedded the implementation in the local-cli, you wouldn't be able to enjoy this feature when using old versions of React Native. For example, you wouldn't be able to upgrade from 0.29.2 to 0.38.0 if this new upgrade code was only released in 0.38.0.

Upgrading based on Git is a big improvement in developer experience and it is important to make it available to everyone. By using a separate package react-native-git-upgrade installed globally you can use this new code today no matter what version of React Native your project is using.

One more reason is the recent Yeoman wipeout by Martin Konicek. We didn't want to get these Yeoman dependencies back into the react-native package to be able to evaluate the old template in order to create the patch.

Try it out and provide feedback

As a conclusion, I would say, enjoy the feature and feel free to suggest improvements, report issues and especially send pull requests. Each environment is a bit different and each React Native project is different, and we need your feedback to make this work well for everyone.

Thank you!

I would like to thank the awesome companies Zenika and M6 Web without whom none of this would have been possible!

Introducing Button, Faster Installs with Yarn, and a Public Roadmap

Héctor Ramos

Héctor Ramos

Developer Advocate at Facebook

We have heard from many people that there is so much work happening with React Native, it can be tough to keep track of what's going on. To help communicate what work is in progress, we are now publishing a roadmap for React Native. At a high level, this work can be broken down into three priorities:

  • Core Libraries. Adding more functionality to the most useful components and APIs.
  • Stability. Improve the underlying infrastructure to reduce bugs and improve code quality.
  • Developer Experience. Help React Native developers move faster

If you have suggestions for features that you think would be valuable on the roadmap, check out Canny, where you can suggest new features and discuss existing proposals.

What's new in React Native

Version 0.37 of React Native, released today, introduces a new core component to make it really easy to add a touchable Button to any app. We're also introducing support for the new Yarn package manager, which should speed up the whole process of updating your app's dependencies.

Introducing Button

Today we're introducing a basic <Button /> component that looks great on every platform. This addresses one of the most common pieces of feedback we get: React Native is one of the only mobile development toolkits without a button ready to use out of the box.

Simple Button on Android, iOS

<Button
onPress={onPressMe}
title="Press Me"
accessibilityLabel="Learn more about this Simple Button"
/>

Experienced React Native developers know how to make a button: use TouchableOpacity for the default look on iOS, TouchableNativeFeedback for the ripple effect on Android, then apply a few styles. Custom buttons aren't particularly hard to build or install, but we aim to make React Native radically easy to learn. With the addition of a basic button into core, newcomers will be able to develop something awesome in their first day, rather than spending that time formatting a Button and learning about Touchable nuances.

Button is meant to work great and look native on every platform, so it won't support all the bells and whistles that custom buttons do. It is a great starting point, but is not meant to replace all your existing buttons. To learn more, check out the new Button documentation, complete with a runnable example!

Speed up react-native init using Yarn

You can now use Yarn, the new package manager for JavaScript, to speed up react-native init significantly. To see the speedup please install yarn and upgrade your react-native-cli to 1.2.0:

$ npm install -g react-native-cli

You should now see “Using yarn” when setting up new apps:

Using yarn

In simple local testing react-native init finished in about 1 minute on a good network (vs around 3 minutes when using npm 3.10.8). Installing yarn is optional but highly recommended.

Thank you!

We'd like to thank everyone who contributed to this release. The full release notes are now available on GitHub. With over two dozen bug fixes and new features, React Native just keeps getting better thanks to you.

0.36: Headless JS, the Keyboard API, & more

Héctor Ramos

Héctor Ramos

Developer Advocate at Facebook

Today we are releasing React Native 0.36. Read on to learn more about what's new.

Headless JS

Headless JS is a way to run tasks in JavaScript while your app is in the background. It can be used, for example, to sync fresh data, handle push notifications, or play music. It is only available on Android, for now.

To get started, define your async task in a dedicated file (e.g. SomeTaskName.js):

module.exports = async (taskData) => {
// Perform your task here.
};

Next, register your task in on AppRegistry:

AppRegistry.registerHeadlessTask('SomeTaskName', () =>
require('SomeTaskName')
);

Using Headless JS does require some native Java code to be written in order to allow you to start up the service when needed. Take a look at our new Headless JS docs to learn more!

The Keyboard API

Working with the on-screen keyboard is now easier with Keyboard. You can now listen for native keyboard events and react to them. For example, to dismiss the active keyboard, simply call Keyboard.dismiss():

import { Keyboard } from 'react-native';
// Hide that keyboard!
Keyboard.dismiss();

Animated Division

Combining two animated values via addition, multiplication, and modulo are already supported by React Native. With version 0.36, combining two animated values via division is now possible. There are some cases where an animated value needs to invert another animated value for calculation. An example is inverting a scale (2x --> 0.5x):

const a = Animated.Value(1);
const b = Animated.divide(1, a);
Animated.spring(a, {
toValue: 2,
}).start();

b will then follow a's spring animation and produce the value of 1 / a.

The basic usage is like this:

<Animated.View style={{transform: [{scale: a}]}}>
<Animated.Image style={{transform: [{scale: b}]}} />
<Animated.View>

In this example, the inner image won't get stretched at all because the parent's scaling gets cancelled out. If you'd like to learn more, check out the Animations guide.

Dark Status Bars

A new barStyle value has been added to StatusBar: dark-content. With this addition, you can now use barStyle on both Android and iOS. The behavior will now be the following:

  • default: Use the platform default (light on iOS, dark on Android).
  • light-content: Use a light status bar with black text and icons.
  • dark-content: Use a dark status bar with white text and icons.

...and more

The above is just a sample of what has changed in 0.36. Check out the release notes on GitHub to see the full list of new features, bug fixes, and breaking changes.

You can upgrade to 0.36 by running the following commands in a terminal:

$ npm install --save [email protected]
$ react-native upgrade

Toward Better Documentation

Kevin Lacker

Kevin Lacker

Engineering Manager at Facebook

Part of having a great developer experience is having great documentation. A lot goes into creating good docs - the ideal documentation is concise, helpful, accurate, complete, and delightful. Recently we've been working hard to make the docs better based on your feedback, and we wanted to share some of the improvements we've made.

Inline Examples

When you learn a new library, a new programming language, or a new framework, there's a beautiful moment when you first write a bit of code, try it out, see if it works... and it does work. You created something real. We wanted to put that visceral experience right into our docs. Like this:

import React, { Component } from 'react';
import { AppRegistry, Text, View } from 'react-native';
class ScratchPad extends Component {
render() {
return (
<View style={{flex: 1}}>
<Text style={{fontSize: 30, flex: 1, textAlign: 'center'}}>
Isn't this cool?
</Text>
<Text style={{fontSize: 100, flex: 1, textAlign: 'center'}}>
👍
</Text>
</View>
);
}
}
AppRegistry.registerComponent('ScratchPad', () => ScratchPad);

We think these inline examples, using the react-native-web-player module with help from Devin Abbott, are a great way to learn the basics of React Native, and we have updated our tutorial for new React Native developers to use these wherever possible. Check it out - if you have ever been curious to see what would happen if you modified just one little bit of sample code, this is a really nice way to poke around. Also, if you're building developer tools and you want to show a live React Native sample on your own site, react-native-web-player can make that straightforward.

The core simulation engine is provided by Nicolas Gallagher's react-native-web project, which provides a way to display React Native components like Text and View on the web. Check out react-native-web if you're interested in building mobile and web experiences that share a large chunk of the codebase.

Better Guides

In some parts of React Native, there are multiple ways to do things, and we've heard feedback that we could provide better guidance.

We have a new guide to Navigation that compares the different approaches and advises on what you should use - Navigator, NavigatorIOS, NavigationExperimental. In the medium term, we're working towards improving and consolidating those interfaces. In the short term, we hope that a better guide will make your life easier.

We also have a new guide to handling touches that explains some of the basics of making button-like interfaces, and a brief summary of the different ways to handle touch events.

Another area we worked on is Flexbox. This includes tutorials on how to handle layout with Flexbox and how to control the size of components. It also includes an unsexy but hopefully-useful list of all the props that control layout in React Native.

Getting Started

When you start getting a React Native development environment set up on your machine, you do have to do a bunch of installing and configuring things. It's hard to make installation a really fun and exciting experience, but we can at least make it as quick and painless as possible.

We built a new Getting Started workflow that lets you select your development operating system and your mobile operating system up front, to provide one concise place with all the setup instructions. We also went through the installation process to make sure everything worked and to make sure that every decision point had a clear recommendation. After testing it out on our innocent coworkers, we're pretty sure this is an improvement.

We also worked on the guide to integrating React Native into an existing app. Many of the largest apps that use React Native, like the Facebook app itself, actually build part of the app in React Native, and part of it using regular development tools. We hope this guide makes it easier for more people to build apps this way.

We Need Your Help

Your feedback lets us know what we should prioritize. I know some people will read this blog post and think "Better docs? Pffft. The documentation for X is still garbage!". That's great - we need that energy. The best way to give us feedback depends on the sort of feedback.

If you find a mistake in the documentation, like inaccurate descriptions or code that doesn't actually work, file an issue. Tag it with "Documentation", so that it's easier to route it to the right people.

If there isn't a specific mistake, but something in the documentation is fundamentally confusing, it's not a great fit for a GitHub issue. Instead, post on Canny about the area of the docs that could use help. This helps us prioritize when we are doing more general work like guide-writing.

Thanks for reading this far, and thanks for using React Native!

React Native: A year in review

Martin Konicek

Martin Konicek

Software Engineer at Facebook

It's been one year since we open-sourced React Native. What started as an idea with a handful of engineers is now a framework being used by product teams across Facebook and beyond. Today at F8 we announced that Microsoft is bringing React Native to the Windows ecosystem, giving developers the potential to build React Native on Windows PC, Phone, and Xbox. It will also provide open source tools and services such as a React Native extension for Visual Studio Code and CodePush to help developers create React Native apps on the Windows platform. In addition, Samsung is building React Native for its hybrid platform, which will empower developers to build apps for millions of SmartTVs and mobile and wearable devices. We also released the Facebook SDK for React Native, which makes it easier for developers to incorporate Facebook social features like Login, Sharing, App Analytics, and Graph APIs into their apps. In one year, React Native has changed the way developers build on every major platform.

It's been an epic ride — but we are only getting started. Here is a look back at how React Native has grown and evolved since we open-sourced it a year ago, some challenges we faced along the way, and what we expect as we look ahead to the future.

This is an excerpt. Read the rest of the post on Facebook Code.

React Native for Android: How we built the first cross-platform React Native app

Daniel Witte

Software Engineer at Facebook

Earlier this year, we introduced React Native for iOS. React Native brings what developers are used to from React on the web — declarative self-contained UI components and fast development cycles — to the mobile platform, while retaining the speed, fidelity, and feel of native applications. Today, we're happy to release React Native for Android.

At Facebook we've been using React Native in production for over a year now. Almost exactly a year ago, our team set out to develop the Ads Manager app. Our goal was to create a new app to let the millions of people who advertise on Facebook manage their accounts and create new ads on the go. It ended up being not only Facebook's first fully React Native app but also the first cross-platform one. In this post, we'd like to share with you how we built this app, how React Native enabled us to move faster, and the lessons we learned.

This is an excerpt. Read the rest of the post on Facebook Code.

React Native: Bringing modern web techniques to mobile

Tom Occhino

Tom Occhino

Engineering Manager at Facebook

We introduced React to the world two years ago, and since then it's seen impressive growth, both inside and outside of Facebook. Today, even though no one is forced to use it, new web projects at Facebook are commonly built using React in one form or another, and it's being broadly adopted across the industry. Engineers are choosing to use React every day because it enables them to spend more time focusing on their products and less time fighting with their framework. It wasn't until we'd been building with React for a while, though, that we started to understand what makes it so powerful.

React forces us to break our applications down into discrete components, each representing a single view. These components make it easier to iterate on our products, since we don't need to keep the entire system in our head in order to make changes to one part of it. More important, though, React wraps the DOM's mutative, imperative API with a declarative one, which raises the level of abstraction and simplifies the programming model. What we've found is that when we build with React, our code is a lot more predictable. This predictability makes it so we can iterate more quickly with confidence, and our applications are a lot more reliable as a result. Additionally, it's not only easier to scale our applications when they're built with React, but we've found it's also easier to scale the size of our teams themselves.

Together with the rapid iteration cycle of the web, we've been able to build some awesome products with React, including many components of Facebook.com. Additionally, we've built amazing frameworks in JavaScript on top of React, like Relay, which allows us to greatly simplify our data fetching at scale. Of course, web is only part of the story. Facebook also has widely used Android and iOS apps, which are built on top of disjointed, proprietary technology stacks. Having to build our apps on top of multiple platforms has bifurcated our engineering organization, but that's only one of the things that makes native mobile application development hard.

This is an excerpt. Read the rest of the post on Facebook Code.