title: check for specific gesture recognizer
body: <p>I have uipageviewcontroller which contains VCs. As in any pageviewcontroller you can swipe left, right to change VCs. Everytime the animation finish I add gestureRecognizer to it. My question is how to check does view have specific recognizer or not? I need code like this:</p>
  
  <pre><code>if check view has specific recognizer == false {
   add recognizer
  }else{
  just skip.
  }
  </code></pre>
  
  <p>I am doing it because I have sidebarmenu. When Sidebarmenu appears I want to add gesture for current index pagecontentviewcontroller. So, My code works fine, I just dont want to add gesture everytime the animation finishes.</p>
  
  <p>I am adding code. The problem is my gestures are created in other class(not current). First I am creating the instance of class where I keep gestures:</p>
  
  <pre><code>let transtionManger = TransitionManger()
  </code></pre>
  
  <p>After I add var of this class which is named exitPanGesture:</p>
  
  <pre><code>pageContentViewController.view.addGestureRecognizer(transtionManger.exitPanGesture3)
  </code></pre>
  
  <p>The problem is I add it everytime the view appears. I want to check the existence of gesture before adding it. I dont want to add it everytime. </p>