title: React use this.state or this.props?
body: <p>I'm new to react an got a question about components. 
  I made a component like this: </p>
  
  <pre><code>    class HeaderLabel extends React.Component {
      constructor() {
          super();
      }
  
      componentWillMount() {
          this.setState({ value: String(this.props.value) });
      }
  
      render() {
          return (
              &lt;div&gt;
                  {this.props.value &amp;&amp; this.props.value != "" ? &lt;label className="control-label"&gt;{this.props.value}&lt;/label&gt; : &lt;label className="text-muted"&gt;({Translation.getPhrase("EMPTY")})&lt;/label&gt;}
              &lt;/div&gt;
          );
      }
  }
  
  HeaderLabel.propTypes = {
      value: PropTypes.string
  }
  
  export default HeaderLabel;
  </code></pre>
  
  <p>As you can see I'm using <code>this.props.value</code> to display the value. Is this the right way or is it better to use <code>this.state.value</code>? </p>