Pass props from child to parent react navigation

There is really simple solution to pass back props to parent component on goBack().

You can pass an extra prop containing function to Modal and right before calling goBack() or in componentWillUnmount you can call that function.

Example

export default class SomeComp extends Component {
...

onGoBack = (someDataFromModal) => {
  console.log(someDataFromModal);
}

render() {
    const { navigate } = this.props;
    return (
        <TouchableOpacity
        onPress={navigate("Modal", {data: ..., ..., onGoBack: this.onGoBack})}
        ..../>
       )
    }
}

---

export default class Modal extends Component {
...

componentWillUnmount() {
  if(this.props.navigation.state.params.onGoBack) {
    this.props.navigation.state.params.onGoBack('I fired from Modal!');
  } 
}

render() {
    const { data, ... } = this.props.navigation.state.params;
    const { goBack } = this.props.navigation;
    return (
        <View>
            <TouchableOpacity
            onPress={goBack()}
            ..../>
            <Text>
               {data, ...}
            </Text>
        </View>
       )
    }
}