This project was bootstrapped with Create React Native App.

Below you'll find information about performing common tasks. The most recent version of this guide is available here.

Table of Contents

• Updating to New Releases
• Available Scripts
  • npm start
  • npm test
  • npm run ios
  • npm run android
• Writing and Running Tests
• Environment Variables
  • Configuring Packager IP Address
• Adding Flow
• Customizing App Display Name and Icon
• Sharing and Deployment
  • Publishing to Expo's React Native Community
  • Building an Expo "standalone" app
  • Ejecting from Create React Native App
    • Build Dependencies (Xcode & Android Studio)
    • Should I Use ExpoKit?
• Troubleshooting
  • Networking
  • iOS Simulator won't open
  • QR Code does not scan

Available Scripts

If Yarn was installed when the project was initialized, then dependencies will have been installed via Yarn, and you should probably use it to run these commands as well. Unlike dependency installation, command running syntax is identical for Yarn and NPM at the time of this writing.

npm start

Runs your app in development mode.

Open it in the Expo app on your phone to view it. It will reload if you save edits to your files, and you will see build errors and logs in the terminal.

Sometimes you may need to reset or clear the React Native packager's cache. To do so, you can pass the --reset-cache flag to the start script:

npm start -- --reset-cache
# or
yarn start -- --reset-cache

npm test

Runs the jest test runner on your tests.

npm run ios

Like npm start, but also attempts to open your app in the iOS Simulator if you're on a Mac and have it installed.

npm run android

Like npm start, but also attempts to open your app on a connected Android device or emulator. Requires an installation of Android build tools (see React Native docs for detailed setup). We also recommend installing Genymotion as your Android emulator. Once you've finished setting up the native build environment, there are two options for making the right copy of adb available to Create React Native App:

Using Android Studio's adb

1. Make sure that you can run adb from your terminal.
2. Open Genymotion and navigate to Settings -> ADB. Select “Use custom Android SDK tools” and update with your Android SDK directory.

Using Genymotion's adb

1. Find Genymotion’s copy of adb. On macOS for example, this is normally /Applications/Genymotion.app/Contents/MacOS/tools/.
2. Add the Genymotion tools directory to your path (instructions for Mac, Linux, and Windows).
3. Make sure that you can run adb from your terminal.

Writing and Running Tests

This project is set up to use jest for tests. You can configure whatever testing strategy you like, but jest works out of the box. Create test files in directories called __tests__ or with the .test extension to have the files loaded by jest. See the the template project for an example test. The jest documentation is also a wonderful resource, as is the React Native testing tutorial.

Environment Variables

You can configure some of Create React Native App's behavior using environment variables.

Adding Flow

Flow is a static type checker that helps you write code with fewer bugs. Check out this introduction to using static types in JavaScript if you are new to this concept.

React Native works with Flow out of the box, as long as your Flow version matches the one used in the version of React Native.

To add a local dependency to the correct Flow version to a Create React Native App project, follow these steps:

1. Find the Flow [version] at the bottom of the included .flowconfig
2. Run npm install --save-dev [email protected] (or yarn add --dev [email protected]), where x.y.z is the .flowconfig version number.
3. Add "flow": "flow" to the scripts section of your package.json.
4. Add // @flow to any files you want to type check (for example, to App.js).

Now you can run npm run flow (or yarn flow) to check the files for type errors. You can optionally use a plugin for your IDE or editor for a better integrated experience.

To learn more about Flow, check out its documentation.

Should I Use ExpoKit?

If you have made use of Expo APIs while working on your project, then those API calls will stop working if you eject to a regular React Native project. If you want to continue using those APIs, you can eject to "React Native + ExpoKit" which will still allow you to build your own native code and continue using the Expo APIs. See the ejecting guide for more details about this option.