React.js : communication between components

08 May 2015

One of the best thing about React is, it helps to componentize the whole app. We will divide the whole app into chunks of small components. But when we divide in components then a new issue will arise, communication between different components.

As a reactjs beginner one of the things you should know is communication between different components of the React.js app.

#1 Parent communicating to child

If the want to pass data from parent component to child one, you can pass the data as props.

var Holder = React.createClass({
  render: function() {
    return <span>{this.props.count}</span>;
  }
});

var Incrementer = React.createClass({
  getInitialState: function() {
    return {count: 0};
  },
  handleClick: function() {
    var count = this.state.count + 1;
    this.setState({count: count});
  },
  render: function(){
    return (<div>
      <button onClick={this.handleClick} >Increment</button>
      <Holder count={this.state.count}/>
    </div>)
  }
});

In the above example the Incrementer component is the parent component and Holder is the child component. So we can easily pass the data from parent to child with props.

#2 Without parent-child relationship

Sometimes the components which are not in parent-child relationship might need to communicate, In this case we need to depend on global event system. You can use any pubsub library as you like. Since most project have jQuery, we can use $.trigger and $.on to setup global event system.

In this each component can subscribe to event in componentDidMount lifecycle method and unsubscribe in componentWillUnmount method.

var APP = {};

var Holder = React.createClass({
  getInitialState: function (){
    return {count: 0};
  },
  componentDidMount: function(){
    $(APP).on('up', function(e){
      var count = this.state.count + 1;
      this.setState({count: count});
    }.bind(this));
    
    $(APP).on('down', function(e){
      var count = (this.state.count - 1);
      this.setState({count: count});
    }.bind(this));
  },
  componentWillUnmount: function () {
    $(APP).off('up');
    $(APP).off('down');
  },
  render: function() {
    var count = this.state.count;
    return <span>{count}</span>;
  }
});

var Counter = React.createClass({
  decrement: function() {
    $(APP).trigger('down');
  },
  increment: function() {
    $(APP).trigger('up');
  },
  render: function(){
    return (<div>
      <button onClick={this.increment} >Increment</button>
      <button onClick={this.decrement} >Decrement</button>
    </div>)
  }
});
If you particularly enjoy my work, I appreciate donations given with Gittip.
comments powered by Disqus