62177dbb3b
Summary:When a component prop is set to null/undefined, and doesn't have a default value specified in `getDefaultProps`, the null value is sent over the bridge as a sentinel to reset to the original native value. On iOS this is handled by creating a default view instance for each view type. The default view is then used to look up the unmodified value for any prop that is reset. This is rather expensive however, as it means that for complex views (e.g. WebView, MapView), a minimum of two instances will be created even if only one is needed, and the default view will remain even after all actual view instances have been released. This diff replaces the default view mechanism with a system where the default value of each prop is recorded the first time it is set. This avoids the need to keep an extra copy of the whole view. The only exception is for props that use the `RCT_CUSTOM_VIEW_PROPERTY` macro, which includes the default view as part of the interface. To avoid a breaking change, a default view will still be created for views that use this macro, but only if they are sent a null value (so very rarely, in practice). In a future update we may deprecate or replace `RCT_CUSTOM_VIEW_PROPERTY` if there are significant benefits to doing so. Reviewed By: javache Differential Revision: D3012115 fb-gh-sync-id: 259348e54aa8342f444ad182b6f883d2dd684973 shipit-source-id: 259348e54aa8342f444ad182b6f883d2dd684973
React Native 
React Native enables you to build world-class application experiences on native platforms using a consistent developer experience based on JavaScript and React. The focus of React Native is on developer efficiency across all the platforms you care about - learn once, write anywhere. Facebook uses React Native in multiple production apps and will continue investing in React Native.
Supported operating systems are >= Android 4.1 (API 16) and >= iOS 7.0.
- Getting Started
- Getting Help
- Documentation
- Examples
- Extending React Native
- Upgrading
- Opening Issues
- Contributing
- License
Introduction
See the official React Native website for an introduction to React Native.
Getting Started
- Follow the Getting Started guide to install React Native and its dependencies.
- Check out this tutorial to walk through your first project that fetches real data and displays it in a list.
- Open the UIExplorer example project to see a list of components that ship with React Native.
- Install the React Developer Tools for Chrome or Firefox for better debugging (read more).
- Try out apps from the Showcase to see what React Native is capable of!
Getting Help
Please use these community resources for getting help. We use the GitHub issues for tracking bugs and feature requests and have limited bandwidth to address them.
- Ask a question on StackOverflow and tag it with
react-native - Chat with us on Reactiflux in #react-native
- Articulate your feature request or upvote existing ones on Product Pains
- Start a thread on the React Discussion Board
- Join #reactnative on IRC: chat.freenode.net
- If it turns out that you may have found a bug, please open an issue
Documentation
The website’s documentation is divided into multiple sections.
- There are Guides that discuss topics like debugging, integrating with existing apps, and the gesture responder system.
- The Components section covers React components such as
ViewandNavigator. - The APIs section covers other libraries like Animated and StyleSheet that aren’t React components themselves.
- Finally, React Native provides a small number of Polyfills that offer web-like APIs.
Another great way to learn more about the components and APIs included with React Native is to read their source. Look under the Libraries directory for components like ScrollView and Navigator, for example. The UIExplorer example is also here to demonstrate some of the ways to use these components. From the source you can get an accurate understanding of each component’s behavior and API.
The React Native documentation only discusses the components, APIs and topics specific to React Native (React on iOS and Android). For further documentation on the React API that is shared between React Native and React DOM, refer to the React documentation.
Examples
git clone https://github.com/facebook/react-native.gitcd react-native && npm install
Running the examples on iOS
Now open any example (the .xcodeproj file in each of the Examples subdirectories) and hit Run in Xcode.
Running the examples on Android
Note that you'll need the Android NDK installed, see prerequisites.
./gradlew :Examples:Movies:android:app:installDebug
# Start the packager in a separate shell (make sure you ran npm install):
./packager/packager.sh
# Open the Movies app in your emulator
Extending React Native
- Looking for a component? JS.coach
- Fellow developers write and publish React Native modules to npm and open source them on GitHub.
- Making modules helps grow the React Native ecosystem and community. We recommend writing modules for your use cases and sharing them on npm.
- Read the guides on Native Modules (iOS, Android) and Native UI Components (iOS, Android) if you are interested in extending native functionality.
Upgrading
React Native is under active development. See the guide on upgrading React Native to keep your project up-to-date.
Opening Issues
If you encounter a bug with React Native we would like to hear about it. Search the existing issues and try to make sure your problem doesn’t already exist before opening a new issue. It’s helpful if you include the version of React Native and OS you’re using. Please include a stack trace and reduced repro case when appropriate, too.
The GitHub issues are intended for bug reports and feature requests. For help and questions with using React Native please make use of the resources listed in the Getting Help section. Product Pains in particular is a good way to signal your interest in a feature or issue. There are limited resources available for handling issues and by keeping the list of open issues lean we can respond in a timely manner.
Contributing
For more information about contributing PRs and issues, see our Contribution Guidelines.
Good First Task is a great starting point for PRs.
We encourage the community to ask and answer questions on Stack Overflow with the react-native tag. It's a great way to help out and be involved!
License
React is BSD licensed. We also provide an additional patent grant.
React documentation is Creative Commons licensed.
Examples provided in this repository and in the documentation are separately licensed, as are some of the custom components.