title: Unable to perform onPress in ReactNative nested component
body: <p>So I am using react native and an unable to get the function to be called onPress. I have a SearchUser component which has a render method within which I have called</p>
  
  <pre><code>&lt;ShowUsers allUsers={this.state.details} access_token={this.state.access_token}/&gt;
  </code></pre>
  
  <p>Now the ShowUsers is as follows</p>
  
  <pre><code>class ShowUsers extends Component{ 
  ....
  render(){
  var user = this.state.details;
  var userList = user.map(function(user,index){
        var img={
          uri:user.avatar.uri,
        }
        return(
          &lt;ListItem icon  key={ index }&gt;
                &lt;Left&gt;
                  &lt;Thumbnail small source={img} /&gt;
                &lt;/Left&gt;
                &lt;Body&gt;
                &lt;Text&gt;{"@"+user.uname+" "+user.id}&lt;/Text&gt;
                  &lt;Text note&gt;{user.fname+" "+user.lname}&lt;/Text&gt;
                &lt;/Body&gt;
                &lt;Right&gt;
                    &lt;Icon style={{fontSize:30}} name="ios-add-circle" onPress={this.followThem(user.id).bind(this)} /&gt;
                &lt;/Right&gt;
            &lt;/ListItem&gt;
          );
        });
        return(
          &lt;View&gt;
           {userList}
         &lt;/View&gt;);
      }
  
  followThem(userId){
    Alert.alert("userId "+userId);
   }
  </code></pre>
  
  <p>When I click the icon I get the following errror 
  undefined is not a function (evaluating this.followThem(user.id))</p>
  
  <p>As far as I understand the value of this is undefined however I have used functions such as the one below in my SearchUser component. Which calls the function properly</p>
  
  <pre><code> &lt;Icon onPress={this.goBack.bind(this)} name="arrow-back" /&gt;
  </code></pre>
  
  <p>I have also tried this.followThem.bind(this,user.id) but to no avail what am I doing wrong?</p>