How to pass props value to other components that doesn't have parent-child relationship in React?

Question

I would like to pass value of the props when user click on a particular topic which is "this.props.topicID" to other components. However, its giving undefined error when I try to access from other components. How can we set the props scope to global in order to access from other components.

    var MainContainer = React.createClass({

    render: function() {    
        return (
            <div className="container">
                <TopicsList />

            </div>
        );
    }
});


var TopicsList = React.createClass({

    getInitialState: function () {
        return {
            isTopicClicked : false,
            topicPages
        };
    },

    onClick: function (event) {
        this.setState({isTopicClicked : true});
    },

    render: function () {
        return (
            <div>
                <div className="row topic-list">
                    <SingleTopicBox 
                        topicID="1" 
                        onClick={this.onClick} 
                        label="Topic"
                        />
                    <SingleTopicBox 
                        topicID="2" 
                        onClick={this.onClick} 
                        label="Topic"
                        />
                    <SingleTopicBox 
                        topicID="3" 
                        onClick={this.onClick} 
                        label="Topic"
                        />
                    <SingleTopicBox 
                        topicID="4" 
                        onClick={this.onClick} 
                        label="Topic"
                        />
                </div>
                <div className="row">
                    { this.state.isTopicClicked ? <SelectedTopicPage topicPages={topicPages} /> : null }
                </div>
            </div>
        );
    }
});


var SingleTopicBox = React.createClass({

    render: function () {
        return (
            <div>
                <div className="col-sm-2">
                    <div onClick={this.props.onClick.bind(null, this)} className="single-topic" data-topic-id={this.props.topicID}>
                        {this.props.label} {this.props.topicID}
                    </div>
                </div>
            </div>
        );
    }
});

var topicPages = [
    { 
        topic_no: '1',
        topic_page_no: '1',
        headline: 'Topic 1 headline', 
        description: 'Topic 1 description comes here...', 
        first_topic_page: true,
        last_topic_page: false
    },
    { 
        topic_no: '2',
        topic_page_no: '2',
        headline: 'Topic 2 headline', 
        description: 'Topic 2 description comes here...', 
        first_topic_page: false,
        last_topic_page: false
    },
    { 
        topic_no: '3',
        topic_page_no: '3',
        headline: 'Topic 3 headline', 
        description: 'Topic 3 description comes here...', 
        first_topic_page: false,
        last_topic_page: false
    },
    { 
        topic_no: '4',
        topic_page_no: '4',
        headline: 'Topic 4 headline', 
        description: 'Topic 4 description comes here...', 
        first_topic_page: false,
        last_topic_page: true
    }
];

var SelectedTopicPage = React.createClass({

    render: function() {
        return (
            <div>
                {this.props.topicPages.filter(function(topicPage) {
                    return topicPage.topic_no === '2'; // if condition is true, item is not filtered out
                }).map(function (topicPage) {
                    return (
                        <SelectedTopicPageMarkup headline={topicPage.headline} key={topicPage.topic_no}>
                            {topicPage.description}
                        </SelectedTopicPageMarkup> 
                    );
                })}
            </div>
        );
    }
});


var SelectedTopicPageMarkup = React.createClass({

    render: function() {    
        return (
            <div className="topics-page">
                <h1>{this.props.headline}</h1>
                <p>{this.props.children}</p>
            </div>
        );
    }
});


ReactDOM.render(<MainContainer />, document.getElementById('main-container'));

Answer 1

It looks like the onClick method of TopicsList should actually be something like:

onClick: function (childBoxWithClick) {
  this.setState({
    isTopicClicked : true,
    lastClickedTopicId: childBoxWithClick.props.topicID
  });
},

Then the parent TopicsList component can pass that info as a prop into it's other children.

However it's a bit wanky to push whole component up to a parent. So you might want to modify the

<div onClick={this.props.onClick.bind(null, this)} ... >

to something more specific like:

<div onClick={this.props.onClick.bind(null, this.props.topicId)} ... >

This should work fine in this example, but a more complex case may want to use a Flux construction, if the data truly needs to be globally accessed throughout the app.