title: Get an attribute value of touchableOpacity tag onPress in React Native
body: <p>I'm new in react native I have a question. I want to create my own picker.
  So I tried to list my Items one by one in a TouchableOpacity so when user touched an item I can get it's value.</p>
  
  <pre><code>&lt;TouchableOpacity key={12} lable='12' style={{margin:3}} onPress={() =&gt; this._helloXP(this.key)} &gt;
  </code></pre>
  
  <p>How can I achive this?
  is there a way to get an attributes value of a tag by pressing?
  in above example I want to get key and lable value by pressing.</p>