UITapGestureRecognizer not working if tapping same location for two separate UIImageViews

Question

I'm attaching a UITapGestureRecognizer to two different imageviews that will occupy the same space but at different times. Currently I'm using a flip transition that when an image is tapped it flips to the image on the other side like a card flipping over. I can get the first image to flip just fine but once flipped the second image doesn't respond at all when being tapped. I used a print("tapped") to see if the second image is even getting the tap gesture but it isn't. This is the function I used to add the tap gestures:

  func addTapGestures() {

    jokerImageView.isUserInteractionEnabled = true
    vendettaImageView.isUserInteractionEnabled = true

    let tap = UITapGestureRecognizer(target: self, action: #selector(flipView(_:)))
    jokerImageView.addGestureRecognizer(tap)
    vendettaImageView.addGestureRecognizer(tap)

  }

Answer 1

The UITapGestureRecognizer is a distinct object. It can only be added to one element at a time.

So in your code, you add it to jokerImageView and then immediately remove it and add it to vendettaImageView.

You either need to create 2 instances of UITapGestureRecognizer, or you need to add it to joker after it has been "used" by vendetta and vice-versa.

Edit: Instead of creating a 2nd gesture recognizer, you could try this:

func flipView(_ sender: Any) -> Void {

    // view flip code goes here

    // then
    if let g = sender as? UIGestureRecognizer {
        if g.view == vendettaImageView {
            jokerImageView.addGestureRecognizer(g)
        } else {
            vendettaImageView.addGestureRecognizer(g)
        }
    }
}