J.Doe J.Doe - 12 days ago 7
React JSX Question

How to access child components value (in a ListView) in parent component in React Native

My app has a list view that render a list of items.

Screenshot

Every click of my child component triggers a change in state value

{ selected: !this.state.selected }


In the image above I have selected 2 child items, how can I access their value in my parent component?

For instance,

Big Data: true
IoT: true


This is my parent snippet, Hosted on Github too

import InterestItem from './InterestItem';

class AddInterest extends Component {

componentWillMount() {
this.createDataSource(this.props);
}

componentWillReceiveProps(nextProps) {
this.createDataSource(nextProps);
}

createDataSource({ items }) {
const ds = new ListView.DataSource({
rowHasChanged: (r1, r2) => r1 !== r2
});
this.dataSource = ds.cloneWithRows(items);
}

//return arrays of event from events
renderRow(item) {
return <InterestItem item={item} icon={computer} />;
}

render() {
const { centerEverything, skeleton, container, textContainer, contentContainer, listViewContainer,
titleContainer, descContainer, title, desc, submitContainer, submitTitle } = styles;
return (
<View style={[container]}>
<View style={[centerEverything, textContainer]}>
<View style={titleContainer}>
<Text style={[title]}>What kind of events are you interest in?</Text>
</View>
<View style={descContainer}>
<Text style={[desc]}>You'll see more events from the categories you choose.</Text>
</View>
</View>

<View style={[contentContainer]}>
<ListView
enableEmptySections
contentContainerStyle={listViewContainer}
dataSource={this.dataSource}
renderRow={this.renderRow}
/>
</View>

<View style={[centerEverything, {paddingBottom: 10}]}>
<View style={[centerEverything, submitContainer]}>
<Text style={submitTitle}>Submit</Text>
</View>
</View>

</View>
)
}
}


This is my child component, Hosted on GitHub too

class InterestItem extends Component {

state = {
selected: false
}

render() {
const { skeleton, centerEverything, container, textStyle } = styles;
return(
<TouchableWithoutFeedback onPress={() => this.setState({ selected: !this.state.selected })}>
<View style={[centerEverything, container, { backgroundColor: this.state.selected ? '#635eb4' : '#e7e7e7'}]}>
{this.props.icon}
<Text style={textStyle}>{this.props.item[0]}</Text>
</View>
</TouchableWithoutFeedback>
)
}
}


Upon request from @freesoul, here's the child instances (considering I have 8 children)
enter image description here

Answer

Following up on @free-soul, I would do the following modifications to your code:

constructor(){
    this.state = {
    //...
        rowStates = {} // Holds the state for each row, identified by the uid property (I'm assuming it is unique, otherwise use some other value)
    }
    this.renderRow = this.renderRow.bind(this);
    this.rowUpdated = this.rowUpdated.bind(this);
}
renderRow(item) {
   // Adds a callback so that we know when an element has been pressed
    return <InterestItem item={item} icon={computer} onPress={this.rowUpdated(item)}/>;
}

rowUpdated(item){
     let rowStates = {...this.state.rowStates}; // Make a copy of the object
     rowStates[item.uid] = !rowStates[item.uid];  // If the item is not in the object, !undefined will be evaluated, which results in true, so the operation is safe
     this.setState({rowStates});
}

Then, your child component should look like this:

class InterestItem extends Component {

  state = {
    selected: false
  }

  render() {
    const { skeleton, centerEverything, container, textStyle } = styles;
    return(
      <TouchableWithoutFeedback onPress={() => {this.setState({ selected: !this.state.selected }); if(this.props.onPress) this.props.onPress(this.props.item)}}>
        <View style={[centerEverything, container, { backgroundColor: this.state.selected ? '#635eb4' : '#e7e7e7'}]}>
          {this.props.icon}
          <Text style={textStyle}>{this.props.item[0]}</Text>
        </View>
      </TouchableWithoutFeedback>
    )
  }
}

Hope it helps