react-native/docs/EmbeddedAppIOS.md

---
id: embedded-app-ios
title: Integrating with Existing Apps
layout: docs
category: Guides (iOS)
permalink: docs/embedded-app-ios.html
next: communication-ios
---

Since React makes no assumptions about the rest of your technology stack – it’s commonly noted as simply the `V` in `MVC` – it’s easily embeddable within an existing non-React Native app. In fact, it integrates with other best practice community tools like [CocoaPods](http://cocoapods.org/).

## Requirements

- [CocoaPods](http://cocoapods.org/) – `gem install cocoapods`
- [Node.js](http://nodejs.org)
  - Install **nvm** with [its setup instructions here](https://github.com/creationix/nvm#installation). Then run `nvm install node && nvm alias default node`, which installs the latest version of Node.js and sets up your terminal so you can run it by typing `node`.  With nvm you can install multiple versions of Node.js and easily switch between them.
- Install the `react-native` package from npm by running the following command in the root directory of your project:
  - `npm install react-native`

At this point you should have the React Native package installed under a directory named `node_modules` as a sibling to your `.xcodeproj` file.


## Install React Native Using CocoaPods

[CocoaPods](http://cocoapods.org/) is a package management tool for iOS/Mac development. We need to use it to download React Native. If you haven't installed CocoaPods yet, check out [this tutorial](http://guides.cocoapods.org/using/getting-started.html).

When you are ready to work with CocoaPods, add the following lines to `Podfile`. If you don't have one, then create it under the root directory of your project.

```ruby
# Depending on how your project is organized, your node_modules directory may be
# somewhere else; tell CocoaPods where you've installed react-native from npm
pod 'React', :path => './node_modules/react-native', :subspecs => [
  'Core',
  'RCTImage',
  'RCTNetwork',
  'RCTText',
  'RCTWebSocket',
  # Add any other subspecs you want to use in your project
]
```

Remember to install all subspecs you need. The `<Text>` element cannot be used without the `RCTText` subspec, for example.

Then install your pods:

```
$ pod install
```

## Create Your React Native App

There are two pieces you’ll need to set up:

1. The root JavaScript file that will contain your actual React Native app and other components
- Wrapper Objective-C code that will load up your script and create a `RCTRootView` to display and manage your React Native components

First, create a directory for your app’s React code and create a simple `index.ios.js` file:

```
$ mkdir ReactComponent
$ touch ReactComponent/index.ios.js
```

Copy & paste following starter code for `index.ios.js` – it’s a barebones React Native app:

```
'use strict';

import React, {
  Text,
  View
} from 'react-native';

var styles = React.StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: 'red'
  }
});

class SimpleApp extends React.Component {
  render() {
    return (
      <View style={styles.container}>
        <Text>This is a simple application.</Text>
      </View>
    )
  }
}

React.AppRegistry.registerComponent('SimpleApp', () => SimpleApp);
```

`SimpleApp` will be your **module name**, which will be used later on.

## Add Container View To Your App

You should now add a container view for the React Native component. It can be any `UIView` in your app.

![Container view example](img/EmbeddedAppContainerViewExample.png)

However, let's subclass `UIView` for the sake of clean code. Let's name it `ReactView`. Open up `Yourproject.xcworkspace` and create a new class `ReactView` (You can name it whatever you like :)).

```
// ReactView.h

#import <UIKit/UIKit.h>
@interface ReactView : UIView
@end
```

In a view controller that wants to manage this view, go ahead and add an outlet and wire it up:

```
// ViewController.m

@interface ViewController ()
@property (weak, nonatomic) IBOutlet ReactView *reactView;
@end
```
__NOTE__ For Swift apps there is no need for that.

Here I disabled **AutoLayout** for simplicity. In real production world, you should turn on AutoLayout and setup constraints by yourself.

## Add RCTRootView To Container View

Ready for the most interesting part? Now we shall create the `RCTRootView`, where your React Native app lives.

In `ReactView.m`, we need to first initiate `RCTRootView` with the URI of your `index.ios.bundle`. `index.ios.bundle` will be created by packager and served by React Native server, which will be discussed later on.

```
NSURL *jsCodeLocation = [NSURL URLWithString:@"http://localhost:8081/index.ios.bundle?platform=ios"];
// For production use, this `NSURL` could instead point to a pre-bundled file on disk:
//
//   NSURL *jsCodeLocation = [[NSBundle mainBundle] URLForResource:@"main" withExtension:@"jsbundle"];
//
// To generate that file, run the curl command and add the output to your main Xcode build target:
//
//   curl http://localhost:8081/index.ios.bundle -o main.jsbundle
RCTRootView *rootView = [[RCTRootView alloc] initWithBundleURL:jsCodeLocation
                                                    moduleName: @"SimpleApp"
                                             initialProperties:nil
                                                 launchOptions:nil];
```

Then add it as a subview of the `ReactView`.

```
[self addSubview:rootView];
rootView.frame = self.bounds;
```

### Swift apps

Add the following to ReactView.swift file:

```
import UIKit
import React

class ReactView: UIView {

  let rootView: RCTRootView = RCTRootView(bundleURL: NSURL(string: "http://localhost:8081/index.ios.bundle?platform=ios"),
    moduleName: "SimpleApp", initialProperties: nil, launchOptions: nil)

  override func layoutSubviews() {
    super.layoutSubviews()

    loadReact()
  }

  func loadReact () {
        addSubview(rootView)
        rootView.frame = self.bounds
  }
}
```

And then make sure your view is added in a ViewContainer or story board file.

## Start Development Server

In root directory, we need to start React Native development server.

```
(JS_DIR=`pwd`/ReactComponent; cd node_modules/react-native; npm run start -- --root $JS_DIR)
```

This command will start up a React Native development server within our CocoaPods dependency to build our bundled script. The `--root` option indicates the root of your React Native apps – this will be our `ReactComponent` directory containing the single `index.ios.js` file. This running server will package up the `index.ios.bundle` file accessible via `http://localhost:8081/index.ios.bundle`.

## Update App Transport Security

On iOS 9 and above the app won't be a able to connect over http to localhost unless specifically told so. See this thread for alternatives and instructions: http://stackoverflow.com/questions/31254725/transport-security-has-blocked-a-cleartext-http.

It is recommended that you add an App Transport Security exception for `localhost` in your app's `Info.plist` file:

```xml
<key>NSAppTransportSecurity</key>
<dict>
    <key>NSExceptionDomains</key>
    <dict>
        <key>localhost</key>
        <dict>
            <key>NSTemporaryExceptionAllowsInsecureHTTPLoads</key>
            <true/>
        </dict>
    </dict>
</dict>
```

If you don't do this, you will see the error - `Could not connect to development server.` when connecting to your server over http.

## Compile And Run

Now compile and run your app. You shall now see your React Native app running inside of the `ReactView`.

![Example](img/EmbeddedAppExample.png)

Live reload and all of the debugging tools will work from the simulator (make sure that DEBUG=1 is set under Build Settings -> Preprocessor Macros).  You've got a simple React component totally encapsulated behind an Objective-C `UIView` subclass.

## Conclusion

So under the hood, when `RCTRootView` is initialized, it will try to download, parse and run the bundle file from React Native development server. This means all you need to do is to implement your own container view or view controller for the `RCTRootView` – the `RCTRootView` ingests your bundled JS and renders your React components. Bravo!

You can checkout full source code of a sample application [here](https://github.com/hfossli/ReactNativeIntegration).