title: textDocumentProxy only applicable in KeyboardViewController.swift?
body: <p>I am trying to create a custom keyboard extension that pushes to another <code>UIViewController</code> that has a list of text that can be inserted onto the selected text field. It subclasses a <code>UIInputViewController</code>. However, when I try to use the <code>textDocumentProxy</code> to input text on <code>didSelectRowAtIndexPath()</code> nothing seems to be happening. </p>
  
  <p>Does the <code>textDocumentProxy</code> only apply to the default <code>KeyboardViewController.swift</code> file that was generated or am I able to to create another <code>UIViewController</code> that subclasses <code>UIInputViewController</code> to insert text? My last resort would be to use delegation or create a listener that will call a function in <code>KeyboardViewController.swift</code>, but I just wanted to see if anyone knew a better way.</p>
  
  <p>Thanks in advance! </p>
  
  <p><strong>Code example is shown below:</strong> </p>
  
  <pre><code>import UIKit
  
  class AnotherInputViewController: UIInputViewController, UITableViewDelegate, UITableViewDataSource {
  
  ...
  
  func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
      tableView.deselectRowAtIndexPath(indexPath, animated: false)
      var proxy = textDocumentProxy as UITextDocumentProxy
  
      if let input = arrayTextToInput[indexPath.row] as? String {
          proxy.insertText(input)
      }
  }
  
  }
  </code></pre>