title: addGestureRecognizer not firing if statement in swift4
body: <p>I am trying to use a if statement when the uses touches the imageview it changes the constraints. Right now my code changes from small to big but it does not change from big to small. So the if statement only works one time but does not work again. </p>
  
  <pre><code> var counter = 0
  
      override func viewDidAppear(_ animated: Bool) {
          super.viewDidAppear(animated)
  
          let tap = UITapGestureRecognizer(target: self, action: #selector(ViewController.handleRegisterC))
          FIRE.addGestureRecognizer(tap)
          FIRE.isUserInteractionEnabled = true
          print(counter)
  
      }
  override func viewDidLoad() {
      super.viewDidLoad()
      // Do any additional setup after loading the view, typically from a nib.
  
          view.addSubview(FIRE)
      FIRE.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
      FIRE.topAnchor.constraint(equalTo: view.topAnchor, constant: 0).isActive = true
  
  
  
      FIRE.widthAnchor.constraint(equalToConstant: 400).isActive = true
      FIRE.heightAnchor.constraint(equalToConstant: 700).isActive = true
       FIRE.translatesAutoresizingMaskIntoConstraints = false
  
  
  
      @objc func handleRegisterC(sender: UIButton){
  
          counter += 1
  
  
          if counter % 2 == 0 {
  
  
              FIRE.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
              FIRE.topAnchor.constraint(equalTo: view.topAnchor, constant: 0).isActive = true
  
  
              FIRE.widthAnchor.constraint(equalToConstant: 400).isActive = true
              FIRE.heightAnchor.constraint(equalToConstant: 700).isActive = true
              FIRE.translatesAutoresizingMaskIntoConstraints = false
  
          }
          if counter % 2 == 1 {
              FIRE.topAnchor.constraint(equalTo: view.topAnchor, constant: 0).isActive = true
              FIRE.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: 0).isActive = true
              FIRE.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 0).isActive = true
              FIRE.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: 0).isActive = true
              FIRE.translatesAutoresizingMaskIntoConstraints = false
  
  
          }
  
  
      }
  
  
  
  }
  </code></pre>