React.js: attach event from parent to children

Question

as shown in the example below, I'd like MyComponent to dynamically attach an "onClick" event to its children. The onClick event should fire alertView that should be able to call the clicked element method "getValue".

JSFiddle: http://jsfiddle.net/2g638bp8/

How to do this? Thanks

var MyComponent = React.createClass({
    alertValue: function () {
        // RETRIEVE THE CHILD HERE
        alert(child.getValue());
    },
    render: function () {
        var children = React.Children.map(this.props.children, function (c, index) {
            return React.addons.cloneWithProps(c, {
                ref: 'child-' + index
            });
        });
        return (
            <div>
                {children}
            </div>
        );
    }
});

var MySubComponent = React.createClass({
    getValue: function () {
        return this.props.val;
    },
    render: function () {
        return (
            <div>{this.props.val}</div>
        );
    }
});

React.render(
    <div>
        <MyComponent>
            <MySubComponent val="1" />
            <MySubComponent val="2" />
            <MySubComponent val="3" />
        </MyComponent>
    </div>,
    document.getElementById('container')
);

Answer 1

You can't call methods on child components in React. You can only set properties. (The child is actually a ReactElement which contains information about the class and associated properties. It is not an instance of the component you created).

So, you could think about this a slightly different way and move the onClick to the MySubComponent:

var MyComponent = React.createClass({
    onHandleGiveValue: function (value) {
        alert(value);
    },
    render: function () {
        const children = React.Children.map(this.props.children, child => React.cloneElement(child, { onGiveValue: this.onHandleGiveValue.bind(this) }));
        return (
            <div>
                {children}
            </div>
        );
    }
});

var MySubComponent = React.createClass({
    handleClick: function() {
        this.props.onGiveValue(this.props.val);
    },
    getValue: function () {
        return this.props.val;
    },
    render: function () {
        return (
            <div onClick={ this.handleClick } >{this.props.val}</div>
        );
    }
});

React.render(
    <div>
        <MyComponent>
            <MySubComponent val="1" />
            <MySubComponent val="2" />
            <MySubComponent val="3" />
        </MyComponent>
    </div>,
    document.getElementById('container')
);

By doing that, your code can pass the current value as an event to the parent component. I've created a new event from the MySubComponent class named onGiveValue. That for now just passes the value from this.props.val. But, it could of course be anything.