在 componentDidUpdate 错误中反应本机调用 setState

Question

I've a multiscreen app using react-navigation and passing a prop from CameraScreen to HomeScreen called 'barcode' like so:

takePicture() {
        //Redirect 
        this.props.navigation.navigate('Home', {barcode: true});
    }

Source: https://reactnavigation.org/docs/en/params.html

On home screen I'm listening for the prop update within componentDidMount and if barcode is true, setState to render a new component like so:

 componentDidUpdate(){
    if(this.props.navigation.getParam('barcode') === true) {
      this.setState({
        barcodeActive: true
      })
    }
  }

I get the error Invariant Violation: Maximum update depth exceeded - from calling setState within componentDidMount. I understand it's in an infinite loop with no break.

How can I listen for when this prop is passed to setState or is there a better way to achieve what I'm after?

Answer 1

You can use prevProps argument, and then compare current and previous values of barcode . If they are not the same, then you can update your state.

 componentDidUpdate(prevProps){
    if(this.props.navigation.getParam('barcode') !== prevProps.navigation.getParam('barcode')) {

      if( this.props.navigation.getParam('barcode')) {
        this.setState({
          barcodeActive: true
        })
       }

    }
  }