index.ios.js

We already saw how we can access the method we exposed from the native module FrequencyDetector. Let's now see how we can use it within our components tree to update the state of our app:

/*** index.ios.js ***/

...

var FrequencyDetector = NativeModules.FrequencyDetector;

export default class guitarTuner extends Component {

  ...
 
  componentWillMount() {
    FrequencyDetector.initialise();
    setInterval(() => {
      FrequencyDetector.getFrequency((res, freq) => {
        let stringData = getClosestString(parseInt(freq));
        if(!stringData) {
          this.setState({
            delta: null,
            activeString: null
          });
        } else {
          this.setState({
            delta: stringData.delta,
            activeString: stringData.number
          });
        }
      });
    }, 500);
  }

 ...
 
});

AppRegistry.registerComponent('guitarTuner', () => guitarTuner);

Most of the logic will be placed in the componentWillMount method of our...