onError in img tag in React

Question

I want to replace a broken link with a default image in react. I'd typically use onerror for this but it is not working as expected. Specifically, I get repeated errors of "Cannot update during an existing state transition (such as within render)." Eventually, the default image appears, but it takes a long time (many prints of this error). This is a very similar question asked here: react.js Replace img src onerror. I tried this solution (top one, not using jQuery) but it causes the error described. I guess onError must be getting triggered continually, thus causing the constant rerendering. Any alternative solutions/fixes?

   import React from 'react';
import { connect } from 'react-redux';
//import AddImageModal from '../components/AddImageModal.js';
import Button from 'react-bootstrap/lib/Button';
//import { getPostsByUserId } from 'actions'
import Posts from '../components/Posts.js';
var Modal = require('react-modal');
require('../../styles/AddImageModal.scss');
import { save_post } from '../actions';

 const customStyles = {
  content : {
    top                   : '50%',
    left                  : '50%',
    right                 : 'auto',
    bottom                : 'auto',
    marginRight           : '-50%',
    transform             : 'translate(-50%, -50%)'
  }
};

var MyWallScreen = React.createClass({

  getInitialState: function() {
    return { 
      modalIsOpen: false,
      imageUrl: "" 
    };
  },

  openModal: function() {
    this.setState({modalIsOpen: true});
  },

  afterOpenModal: function() {
    // references are now sync'd and can be accessed. 
    this.refs.subtitle.style.color = '#f00';
  },

  closeModal: function() {
    this.setState({modalIsOpen: false});
  },

  setUrl: function(e,val) 
  {
    if (e.keyCode === 13) 
        {
          this.setState({
            imageUrl: val
          });
        }
  },

  resetImageUrl: function()
  {
    this.setState({
      imageUrl: ""
    });
  },

  onError: function() {
    this.setState({
      imageUrl: "default.jpg"
    });
  },


  render: function() {
    const { userPosts, dispatch } = this.props;
    return (
      <div>
        <button onClick={this.openModal}>Add Image</button>

        {/* The meat of the modal. */}
        <Modal
          isOpen={this.state.modalIsOpen}
          onAfterOpen={this.afterOpenModal}
          onRequestClose={this.closeModal}
          style={customStyles} >

        <div className="modalBox">
          <h2 className="modalBanner">Add an image link</h2>
          <input ref="urlInput" 
                className="modalInput"
                onKeyDown={e=>this.setUrl(e,this.refs.urlInput.value)}/>
          {this.state.imageUrl ?
            <img className="modalImage" 
                  src={this.state.imageUrl}
                  onError={this.onError()}/>
            :<div className="modalImage"></div>
          }
          <div>
            <Button className="modalButton" bsStyle = "success" 
                onClick = {() => {
                dispatch(save_post(0,this.state.imageUrl));
                this.closeModal();
                this.resetImageUrl();
                }}>
                Post
            </Button>
            <Button className="modalButton" bsStyle = "danger" 
                onClick = {() => {
                  this.closeModal();
                  this.resetImageUrl();
                }}>
                Cancel
            </Button>
          </div>
        </div>
        </Modal>


        <Posts posts={userPosts}/>
      </div>
    );
  }
});


function mapStateToProps(state, ownProps) {
  return {
    userPosts: state.posts[0]
  }
}


MyWallScreen = connect(mapStateToProps)(MyWallScreen);

export default MyWallScreen;

Answer 1

The code is calling this.onError rather than passing a reference to it. Every call to render is calling this.onError(). Remove the parentheses, and see if that fixes it:

<img className="modalImage" 
  src={this.state.imageUrl}
  onError={this.onError()}/> // `onError` is being called here

Fixed version:

<img className="modalImage" 
  src={this.state.imageUrl}
  onError={this.onError}/> // `onError` is being passed as a reference here