title: Native Base Input Refs Not Being Set
body: <p>So I'm working with the Native Base <code>&lt;Input&gt;</code> tag, trying to set refs to handle "tabbing" through form fields. I've got the following code:</p>
  
  <pre><code>&lt;Item floatingLabel&gt;
    &lt;Label style={{ color: "#fff" }}&gt;First Name&lt;/Label&gt;
    &lt;Input
      ref={input =&gt; {
        this.firstNameRef = input;
      }}
      onSubmitEditing={() =&gt; {
        this.lastNameRef._root.focus();
      }}
      returnKeyType={"next"}
    /&gt;
  &lt;/Item&gt;
  
  &lt;Item floatingLabel last&gt;
    &lt;Label style={{ color: "#fff" }}&gt;Last Name&lt;/Label&gt;
    &lt;Input
      ref={input =&gt; {
        this.lastNameRef = input;
      }}
    /&gt;
  &lt;/Item&gt;
  </code></pre>
  
  <p>So essentially, I have 2 <code>&lt;Input&gt;</code> tags, both with <code>ref</code> set (<code>this.firstNameRef</code> and <code>this.lastNameRef</code>), but on loading the App, pressing First Name, then pressing "next" on the keyboard I get the following error:</p>
  
  <blockquote>
    <p>Cannot read property '_root' of undefined<br/>
    onSubmitEditing<br/>
    <em>Signup.js:162:26</em></p>
  </blockquote>
  
  <p>It seems that using <code>&lt;Input&gt;</code> doesn't actually set any ref values, so <code>this.lastNameRef</code> is <code>null</code>. </p>
  
  <p>I also tried using React Native's <code>&lt;TextInput&gt;</code> element, which does handle setting refs as described above, but still doesn't seem to handle focus after submit (even when removing <code>._root</code> from <code>.focus()</code> logic).</p>
  
  <p>Has anyone else seen this issue?</p>
  
  <p>Note: Only tested in iOS currently.</p>