title: _this._drawer.open is not a function react-native
body: <p>i am using drawer from native base for my react native application. when u click the menu button the drawer not open up and i get this error ( _this._drawer.open ) is not a fucntion what is the isse here is my code </p>
  
  <pre><code>import React, { Component } from 'react';
  import {
  AppRegistry,View
  } from 'react-native';
  import {ScrollableTab,TabHeading, Drawer, Container,Content, Header, 
  Title, Button, Left, Right, Body, Icon ,Text,Tab, Tabs } from 'native-base';
  import SecondStatus from './component/StatusComponent';
  import HeaderComponent from './component/headerComponent';
  import Sports from './component/Sports';
  import MainPage from './component/MainPage';
  import SideBar from './component/SideBar';
  
  export default class Point extends Component {
      closeDrawer = () =&gt; {
      this.drawer.close()
     };
     openDrawer = () =&gt; {
      alert('asasa click');
      console.log('asad--');
      this._drawer.open();
      };
     render() {
  
     return (
            &lt;Container&gt;
             &lt;Drawer
            ref={(ref) =&gt; { this._drawer = ref; }}
            content={&lt;SideBar  /&gt;}
            onClose={() =&gt; this.closeDrawer()} &gt;
  
              &lt;Header  &gt;
                &lt;Left&gt;
                  &lt;Button transparent onPress={this.openDrawer}&gt;
                      &lt;Icon name='arrow-back' /&gt;
                  &lt;/Button&gt;
              &lt;/Left&gt;
              &lt;Body&gt;
                  &lt;Title&gt;UrduPoint&lt;/Title&gt;
              &lt;/Body&gt;
              &lt;Right&gt;
                  &lt;Button transparent onPress=
           {this.openDrawer.bind(this)}&gt;
                          &lt;Icon name='menu' /&gt;
                      &lt;/Button&gt;
              &lt;/Right&gt;
              &lt;/Header&gt;
  
           &lt;/Drawer&gt;
  
  
  
  
          &lt;/Container&gt;
       );
    }
   }
  
  AppRegistry.registerComponent('Point', () =&gt; Point);
  </code></pre>
  
  <p>here is my SideBar.js</p>
  
  <pre><code>  import React, { Component } from 'react';
    import {
   Text,
  View,
   StyleSheet
  } from 'react-native';
  
  export default class SideBar extends Component{
  render(){
      return(
   &lt;View&gt;
     &lt;Text&gt;
       asad
       &lt;/Text&gt;
     &lt;/View&gt;
  
      )
     };
  
   }
  </code></pre>
  
  <p>ps. this drawer is same as in npm 'react-native-drawer'</p>