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

Question

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

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)

Consider a single instance of InterestItem, what can be the value of this.props.item? Can you post an example? — yadhu
– yadhu, Commented Nov 27, 2016 at 12:00
My suggestion is that you should maintain the state of children in your parent; something like state = { cars: false, bigData: true, hackintosh: false, iot: true, ... }. — yadhu
– yadhu, Commented Nov 27, 2016 at 12:29

martinarroyo · Accepted Answer · 2016-11-28 06:01:07Z

2

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

edited Nov 28, 2016 at 6:01

answered Nov 27, 2016 at 18:55

martinarroyo

9,7713 gold badges42 silver badges79 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

J.Doe Over a year ago

I'm afraid rowStates = {} is invalid, react native complains about an error during runtime. State cannot be null?

J.Doe Over a year ago

Thanks for the answer, it was very helpful, though there are 2 mistakes. rowStates: {} and inside renderRow onPress method, we should return in fat arrow function, onPress={() => rowUpdated(item)} otherwise the app will run the method automatically

martinarroyo Over a year ago

Uh, sorry! Didn't notice when writing. I've edited the answer to correct the mistakes.

Collectives™ on Stack Overflow

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

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related