title: Multiple Timer in containerView swift 4 xcode
body: <p>I have one main ControllerView with two container view on top of each other (containerA on top of ContainerB). both containerView has a ControllerView.
  I am running a timer in each ContainerView. problem I am facing is that when I hide ContainerB to show ContainerA, the timer of containerB still running in the background, which is causing over 100% CPU use.</p>
  
  <p>can any please help me how to stop the timer when I have other containerView visible?
  I am using two buttons to hide and show the container views.</p>
  
  <p>ContainerA timer code:</p>
  
  <pre><code>ViewATimer = Timer.scheduledTimer(timeInterval: 1, target: self,   selector: (#selector(self.update)), userInfo: nil, repeats: true)
  </code></pre>
  
  <p>container B:</p>
  
  <pre><code>ViewBTimer = Timer.scheduledTimer(timeInterval: 10, target: self,   selector: (#selector(self.secondUpdate)), userInfo: nil, repeats: true)
  </code></pre>