React setState inside of a function this is undefined
Your inner promise resolution function won't have this context. One way to fix it:
MyAction: function(){ this.doFetch().then(function(response){ this.setState({ the_message: response.message }); }.bind(this))},Read more about that on this StackOverflow question.
A simple .bind(this) would solve the issue:
render: function() {return (<div><div>{this.props.title}</div><br></br><div>{this.props.price}</div><br></br><div onClick={this.MyAction.bind(this)}>{this.props.qty}</div></div>);By adding .bind(this) you keep the scope within your function.