• Expose Component Functions

    Expose Component Functions

    There’s another (uncommon) way of communicating between components: simply expose a method on the child component for the parent to call.

    Say a list of todos, which upon clicking get removed. If there’s only one unfinished todo left, animate it:

    1. var Todo = React.createClass({
    2.   render: function() {
    3.     return <div onClick={this.props.onClick}>{this.props.title}</div>;
    4.   },
    6.   //this component will be accessed by the parent through the `ref` attribute
    7.   animate: function() {
    8.     console.log('Pretend %s is animating', this.props.title);
    9.   }
    10. });
    12. var Todos = React.createClass({
    13.   getInitialState: function() {
    14.     return {items: ['Apple', 'Banana', 'Cranberry']};
    15.   },
    17.   handleClick: function(index) {
    18.     var items = this.state.items.filter(function(item, i) {
    19.       return index !== i;
    20.     });
    21.     this.setState({items: items}, function() {
    22.       if (items.length === 1) {
    23.         this.refs.item0.animate();
    24.       }
    25.     }.bind(this));
    26.   },
    28.   render: function() {
    29.     return (
    30.       <div>
    31.         {this.state.items.map(function(item, i) {
    32.           var boundClick = this.handleClick.bind(this, i);
    33.           return (
    34.             <Todo onClick={boundClick} key={i} title={item} ref={'item' + i} />
    35.           );
    36.         }, this)}
    37.       </div>
    38.     );
    39.   }
    40. });
    42. ReactDOM.render(<Todos />, mountNode);

    Alternatively, you could have achieved this by passing the todo an isLastUnfinishedItem prop, let it check this prop in componentDidUpdate, then animate itself; however, this quickly gets messy if you pass around different props to control animations.