嵌套在React对象prop中的访问对象

Question

I am trying to access a nested object in a React JS prop passed to a component.

this.props.object works when I log it in the console but I get an error saying that a is undefined when I try to access this.props.object.a .

Cannot read property 'source' of undefined
at VenueDetails (VenueDetails.js:8)
at ReactCompositeComponent.js:306
at measureLifeCyclePerf (ReactCompositeComponent.js:75)
at ReactCompositeComponentWrapper._constructComponentWithoutOwner (ReactCompositeComponent.js:305)
at ReactCompositeComponentWrapper._constructComponent (ReactCompositeComponent.js:280)
at ReactCompositeComponentWrapper.mountComponent (ReactCompositeComponent.js:188)
at Object.mountComponent (ReactReconciler.js:46)
at ReactCompositeComponentWrapper.performInitialMount (ReactCompositeComponent.js:371)
at ReactCompositeComponentWrapper.mountComponent (ReactCompositeComponent.js:258)
at Object.mountComponent (ReactReconciler.js:46)

VenueDetailsView.js

import React, { Component } from 'react';
import { connect } from 'react-redux';
import { VenueDetails } from '../presentation';
import { fetchVenue } from '../../redux/actions/venues';

class VenueDetailsView extends Component {
  constructor(props) {
    super(props);
    this.state = {
      venue: {},
    };
  }

  componentDidMount() {
    this.props.fetchVenue(this.props.match.params.id);
  }

  render() {
    return (
      <VenueDetails venue={this.props.selectedVenue}/>
    );
  }
}

const mapStateToProps = (state) => ({
  selectedVenue: state.selectedVenue,
});

export default connect(mapStateToProps, { fetchVenue })(VenueDetailsView);

VenueDetails.js

import React, { PropTypes } from 'react';
import { Card, CardMedia, CardTitle, CardText, CardActions, FlatButton } from 'material-ui';

const VenueDetails = ({ venue }) => {
  return (
    <Card>
      <CardMedia overlay={<CardTitle title={venue.name}/>}>
        <img src={venue.photo.source}/>
          </CardMedia>
            <CardText>
            </CardText>
          <CardActions>
            <FlatButton label="Action1" />
        <FlatButton label="Action2" />
      </CardActions>
    </Card>
  );
};

VenueDetails.propTypes = {
  venue: PropTypes.object.isRequired,
};

export default VenueDetails;

venue.name works as expected but when I try to access venue.photo.source it gives me the above error.

I am new to react and there is probably a simple reason that I am missing.

Answer 1

If the object prop is from some async action, it may be that you're trying to log object.a before object is defined.

Checking that it's defined may solve your problem.

this.props.object && console.log(this.props.object.a)