Child parent component communication in ReactJS

Question

I like to send the attribute properties/props/state values from child component to parent component on an event fire onDrag. I could not find proper documentation on this.

Here is my code:

/*** @jsx React.DOM */
var APP=React.createClass({
  getInitialState:function()
  {
     return {url:'http://www.youtube.com/embed/XGSy3_Czz8k'}
  },
  handleDrag:function(vidurl)
  {
    alert(vidurl);    //i need to get child component url here.
  },
  render:function(){
    return  <div>
               <VideoFrame  src={this.state.url} />
               <hr/>
           <videos handle={this.handleDrag(vidurl)} />
        </div>
  }
});

var VideoFrame=React.createClass({
  render:function(){
    return  <div>
          <iframe width="420" height="315"  src={this.props.src}>
          </iframe>     
        </div>
  }
});

var videos=React.createClass({
  getInitialState:function()
  {
    return {vidurl:'http://www.youtube.com/embed/XGSy3_Czz8k'}
  },
  render:function()
  {
    return  <img src="http://upload.wikimedia.org/wikipedia/en/a/a6/Size_Small.PNG" onDrag={this.props.handle.bind(this.state.vidurl)}></img> //trying to send state value from here
  }
});

React.renderComponent(<APP />, document.body);      

I hope my code is clear.

Answer 1

In App component this line

<videos handle={this.handleDrag(vidurl)} />

is not correct, one should pass the function callback instead of invoke a function.

In VideoForm this line

return  <img src="http://upload.wikimedia.org/wikipedia/en/a/a6/Size_Small.PNG" onDrag={this.props.handle.bind(this.state.vidurl)}></img> //trying to send state value from here

is not correct, this.props.handle is the parent callback, one should just just call this.props.handle(this.state.videoUrl)

Correct Implementation:

var APP = React.createClass({
  getInitialState:function() {
   return {url:'http://www.youtube.com/embed/XGSy3_Czz8k'}
  },

  // Parent callback, pass this function to the child component
  handleDrag:function(videoUrl) {
    alert(videoUrl);
  },

  render: function() {
    return  (
      <div>
         <Videos handle={this.handleDrag} />
      </div>
    );
})


var Videos = React.createClass({

  getInitialState:function()
  {
    return {vidurl:'http://www.youtube.com/embed/XGSy3_Czz8k'}
  },

  handleChanged: function(event) {
    if(this.props.handle) {
      this.props.handle(this.state.videoUrl);
    }
  },

  render:function()
  {
    return  <img src="http://upload.wikimedia.org/wikipedia/en/a/a6/Size_Small.PNG" onDrag={this.handleChanged}></img> //trying to send state value from here
  }
});