react-native-cli is a command line interface that does the rest of the set up. It’s installable via npm. This will install `react-native`as a command in your terminal. You only ever need to do this once.
You can now open this new project (`AwesomeProject/AwesomeProject.xcodeproj`) in Xcode and simply build and run it with cmd+R. Doing so will also start a node server which enables live code reloading. With this you can see your changes by pressing cmd+R in the simulator rather than recompiling in Xcode.
`react-native init` will copy `Examples/SampleProject` to whatever you named your project, in this case AwesomeProject. This is a simple hello world app. You can edit `index.ios.js` to make changes to the app and then press cmd+R in the simulator to see the changes.
Before we write the code to fetch actual Rotten Tomatoes data let's mock some data so we can get our hands dirty with React Native. At Facebook we typically declare constants at the top of JS files, just below the requires, but feel free to add the following constant wherever you like:
We're going to render the title, year, and thumbnail for the movie. Since thumbnail is an Image component in React Native, add Image to the list of React requires below.
Press cmd+R and you should see "Title" above "2015". Notice that the Image doesn't render anything. This is because we haven't specified the width and height of the image we want to render. This is done via styles. While we're changing the styles let's also clean up the styles we're no longer using.
Great, we've rendered our data. Now let's make it look better. I'd like to put the text to the right of the image and make the title larger and centered within that area:
Not too much has changed, we added a container around the Texts and then moved them after the Image (because they're to the right of the Image). Let's see what the style changes look like:
This means that the rightContainer takes up the remaining space in the parent container that isn't taken up by the Image. If this doesn't make sense, add a backgroundColor to rightContainer and then try removing the `flex: 1`. You'll see that this causes the container's size to be the minimum size that fits its children.
Add some initial state to our application so that we can check this.state.movies === null to determine whether the movies data has been loaded or not. We can set this data when the response comes back with this.setState({movies: moviesData}). Add this code just above the render function inside our React class.
We want to send off the request after the component has finished loading. componentDidMount is a function on React components that React will call exactly once just after the component has been loaded.
Implement our fetchData function to actually make the request and handle the response. All you need to do is call this.setState({movies: data}) after resolving the promise chain because the way React works is that setState actually triggers a re-render and then the render function will notice that this.state.movies is no longer null. Note that we call done() at the end of the promise chain - always make sure to call done() or any errors thrown will get swallowed.
Now press cmd+R and you should see "Loading movies..." until the response comes back, then it will render the first movie it fetched from Rotten Tomatoes.
Why is a ListView better than just rendering all of these elements or putting them in a ScrollView? Despite React being fast, rendering a possibly infinite list of elements could be slow. ListView schedules rendering of views so that you only display the ones on screen and those already rendered but off screen are removed from the native view hierarchy.
First thing's first, add the ListView require to the top of the file.
```javascript
var {
AppRegistry,
Image,
ListView,
StyleSheet,
Text,
View,
} = React;
```
Now modify the render funtion so that once we have our data it renders a ListView of movies instead of a single movie.
```javascript
render: function() {
if (!this.state.loaded) {
return this.renderLoadingView();
}
return (
<ListView
dataSource={this.state.dataSource}
renderRow={this.renderMovie}
/>
);
},
```
What is this dataSource thing and why do we use it? This way we can very cheaply know which rows have changed between updates.
You'll notice we added dataSource from this.state. The next step is to add an empty dataSource to getInitialState. Also, now that we're storing the data in dataSource, we should change this.state.movies to be this.state.loaded (boolean) so we aren't storing the data twice.
```javascript
getInitialState: function() {
return {
dataSource: new ListView.DataSource({
rowHasChanged: (row1, row2) => row1 !== row2,
}),
loaded: false,
};
},
```
And here's the modified this.setState in the response handler in fetchData:
There's still some work to be done to make it a fully functional app such as adding navigation, search, infinite scroll loading, etc. Check the [Movies Example](https://github.com/facebook/react-native/tree/master/Examples/Movies) to see it all working.
