Access array of objects to display in React Native Text component

Question

I’m having trouble accessing an array of objects in my JSON data to display in a React Native Text component.

JSON data

{
    "name": "Pizza Joint",
    "when": [{
        "day": ["Sat", "Sun"],
        "start_time": "11:00",
        "end_time": "23:00"
    }]
}

Code

<View style={styles.container}>
    <Text style={styles.name}>{venue.name}</Text>
    <Text style={styles.time}>{venue.when[0].start_time}</Text>
</View>

This throws the error Undefined is not an object (evaluating 'venue.when') which I don't understand since console.log(type of venue.when) returns object.

How can I access the when object properties here?

Additional notes

I copied the app structure from this tutorial.

Here is VenueList.js:

'use strict';

var React = require('react-native');
var VenueDetail = require('./VenueDetail');

var {
    Image,
    StyleSheet,
    Text,
    View,
    Component,
    ListView,
    TouchableHighlight,
    ActivityIndicatorIOS
   } = React;

var styles = StyleSheet.create({
    container: {
        flex: 1,
        flexDirection: 'row',
        justifyContent: 'center',
        alignItems: 'center',
        backgroundColor: '#F5FCFF',
        padding: 10
    },
    thumbnail: {
        width: 53,
        height: 81,
        marginRight: 10
    },
    rightContainer: {
        flex: 1,
    },
    title: {
        fontSize: 20,
        marginBottom: 8
    },
    author: {
        color: '#656565'
    },
    separator: {
        height: 1,
        backgroundColor: '#dddddd'
    },
    listView: {
           backgroundColor: '#F5FCFF'
       },
   loading: {
       flex: 1,
       alignItems: 'center',
       justifyContent: 'center'
   }
});

// var REQUEST_URL = 'https://www.googleapis.com/books/v1/volumes?q=subject:fiction';
var REQUEST_URL = 'http://apib.miniguide.es/wall/today';

class VenueList extends Component {

  render() {
    if (this.state.isLoading) {
      return this.renderLoadingView();
    }
    console.log(this.state.dataSource);

    return (
      <ListView
        dataSource={this.state.dataSource}
        renderRow={this.renderVenue.bind(this)}
        style={styles.listView}
      />
    );
  }

  renderLoadingView() {
    return (
      <View style={styles.loading}>
        <ActivityIndicatorIOS
          size='large'/>
          <Text>
            Loading venues...
          </Text>
      </View>
    );
  }

  constructor(props) {
    super(props);
    this.state = {
      isLoading: true,
      dataSource: new ListView.DataSource({
        rowHasChanged: (row1, row2) => row1 !== row2
      })
    };
  }

  componentDidMount() {
    this.fetchData();
  }

  fetchData() {
    fetch(REQUEST_URL)
    .then((response) => response.json())
    .then((responseData) => {
      this.setState({
        dataSource: this.state.dataSource.cloneWithRows(responseData),
        isLoading: false
      });
    })
    .done();
  }

  renderVenue(venue) {
    console.log(venue);
    return (
      <TouchableHighlight onPress={() => this.showVenueDetail(venue)} underlayColor='#dddddd'>
        <View>
          <View style={styles.container}>
            <Image
//              source={{uri: venue.images[0].url}}
              style={styles.thumbnail} />
            <View style={styles.rightContainer}>
              <Text style={styles.title}>{venue.name}</Text>
              <Text style={styles.author}>{venue.subtitle}</Text>
            </View>
          </View>
          <View style={styles.separator} />
        </View>
      </TouchableHighlight>
    );
  }
}

module.exports = VenueList;

console.log(venue) produces the following format of data (I am simplifying output here for the purposes of the example):

{
    name: 'Pizza Joint',
        when: [{
            day: ['Sat', 'Sun'],
            start_time: '11:00',
            end_time: '23:00'
        }]
}

I notice the above is not JSON since the quotes on the keys have been stripped out.

Solution

Ok I figured it out. The problem was the JSON data set that our API produces has some documents with another definition that delimit the data (e.g. first is document that indicates featured). So React was throwing an error on the first document, which lacked the properties I was attempting to access.

To fix this, I added ternary expressions to the React components to check for the existence of properties:

  renderVenue(venue) {
    console.log(venue);
    return (
      <TouchableHighlight onPress={() => this.showVenueDetail(venue)} underlayColor='#dddddd'>
        <View>
          <View style={styles.container}>
            <Image source={ 'images' in venue ? { uri: 'http://' + venue.images[0].url } : null}       
              style={styles.thumbnail} />
            <View style={styles.rightContainer}>
              <Text style={styles.title}>{venue.name}</Text>
              <Text style={styles.author}>{venue.subtitle}</Text>
              <Text style={styles.author}>{ 'when' in venue ? venue.when[0].start_date : null}</Text>
            </View>
          </View>
          <View style={styles.separator} />
        </View>
      </TouchableHighlight>
    );
  }
}

Perhaps we should modify our API output.

In any event thanks for comments, they were helpful.