Dan Abramov
1f04ff580d
Summary: As we saw in D15947985, and later traced down to D5623623, the `hot` option isn't used by Metro anymore. The relevant transforms _always_ run in DEV regardless of the option. Given that, it doesn't make sense that enabling or disabling Hot Reloading forces a full refresh. This significantly raises the usage barrier because **currently, you might have to wait ~20 seconds (on a large app) to just start using Hot Reloading when you're already in the middle of some screen.** So you just end up not using it. This diff changes enabling/disabling Hot Reloading to be _instant_. Here's how it works: 1. Now we always send the necessary info to the client via the new `HMRClient.setup()` function. It creates a Metro HMR client instance, but only actually sets up the socket if Hot Reloading is on. 2. The "Enable Hot Reloading" menu no longer forces a reload. Instead, it calls `HMRClient.enable()` which lazily sets up a socket (at most once). 3. The "Disable Hot Reloading" menu also doesn't trigger a refresh now. Instead, it calls `HMRClient.disable()`. We don't actually tear down the socket here because it's a pain to deal with race conditions and such. Instead, we keep the connection — but we _ignore the updates_ that come in while we're disabled. 4. As a result, it is possible to enable and disable it many times during a single session. (Updates while disabled would be ignored — which has a risk of making your running app inconsistent — but I'd argue it's expected and is worth it. You can always save a particular file to force it to update once the mode is on.) 5. In order to support "ignoring" updates, Metro's `HMRClient` (not to be confused with RN's module) now supports a `shouldApplyUpdates` field. The RN module uses it to disable handling updates when the mode is off. 6. In case there is an error that makes hot reloading unavailable (such as the server disconnecting), we surface the error only if the mode is on. If the mode is off, we stash the error message in the `_hmrUnavailableReason` variable, and display it next time you try to enable Hot Reloading. Reviewed By: rickhanlonii Differential Revision: D15958160 fbshipit-source-id: 8256fc4d5c2c3f653a78edf13b8515a5671953e4
React Native
Learn once, write anywhere:
Build mobile apps with React.
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React Native brings React's declarative UI framework to iOS and Android. With React Native, you use native UI controls and have full access to the native platform.
- Declarative. React makes it painless to create interactive UIs. Declarative views make your code more predictable and easier to debug.
- Component-Based. Build encapsulated components that manage their own state, then compose them to make complex UIs.
- Developer Velocity. See local changes in seconds. Changes to JavaScript code can be live reloaded without rebuilding the native app.
- Portability. Reuse code across iOS, Android, and other platforms.
React Native is developed and supported by many companies and individual core contributors. Find out more in our ecosystem overview.
Contents
- Requirements
- Building your first React Native app
- Documentation
- Upgrading
- How to Contribute
- Code of Conduct
- License
📋 Requirements
React Native apps may target iOS 9.0 and Android 4.1 (API 16) or newer. You may use Windows, macOS, or Linux as your development operating system, though building and running iOS apps is limited to macOS. Tools like Expo can be used to work around this.
🎉 Building your first React Native app
Follow the Getting Started guide. The recommended way to install React Native depends on your project. Here you can find short guides for the most common scenarios:
📖 Documentation
The full documentation for React Native can be found on our website.
The React Native documentation discusses components, APIs, and topics that are specific to React Native. For further documentation on the React API that is shared between React Native and React DOM, refer to the React documentation.
The source for the React Native documentation and website is hosted on a separate repo, @facebook/react-native-website.
🚀 Upgrading
Upgrading to new versions of React Native may give you access to more APIs, views, developer tools and other goodies. See the Upgrading Guide for instructions.
React Native releases are discussed in the React Native Community, @react-native-community/react-native-releases.
👏 How to Contribute
The main purpose of this repository is to continue evolving React Native core. We want to make contributing to this project as easy and transparent as possible, and we are grateful to the community for contributing bugfixes and improvements. Read below to learn how you can take part in improving React Native.
Code of Conduct
Facebook has adopted a Code of Conduct that we expect project participants to adhere to. Please read the full text so that you can understand what actions will and will not be tolerated.
Contributing Guide
Read our Contributing Guide to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes to React Native.
Open Source Roadmap
You can learn more about our vision for React Native in the Roadmap.
Good First Issues
We have a list of good first issues that contain bugs which have a relatively limited scope. This is a great place to get started, gain experience, and get familiar with our contribution process.
Discussions
Larger discussions and proposals are discussed in @react-native-community/discussions-and-proposals.
📄 License
React Native is MIT licensed, as found in the LICENSE file.
React Native documentation is Creative Commons licensed, as found in the LICENSE-docs file.