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:
var Todo = React.createClass({
render: function() {
return <div onClick={this.props.onClick}>{this.props.title}</div>;
},
//this component will be accessed by the parent through the `ref` attribute
animate: function() {
console.log('Pretend %s is animating', this.props.title);
}
});
var Todos = React.createClass({
getInitialState: function() {
return {items: ['Apple', 'Banana', 'Cranberry']};
},
handleClick: function(index) {
var items = this.state.items.filter(function(item, i) {
return index !== i;
});
this.setState({items: items}, function() {
if (items.length === 1) {
this.refs.item0.animate();
}
}.bind(this));
},
render: function() {
return (
<div>
{this.state.items.map(function(item, i) {
var boundClick = this.handleClick.bind(this, i);
return (
<Todo onClick={boundClick} key={i} title={item} ref={'item' + i} />
);
}, this)}
</div>
);
}
});
React.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.