Gesture recognizer callback over multiple views

Question

I have a custom UIView that consists of 9 equally-sized subviews. It essentially looks like a tic-tac-toe board.

I've added a UIPanGestureRecognizer to this custom view. Each time the user pans over one of the subviews, I want to take an action. For example, the user could pan over the first 3 (of the 9) subviews in one gesture, and in this case I'd want to take 3 actions.

I could try to do some fancy math and figure out the frame of each subview, then figure out when the gesture crosses from one subview to another. However, I feel like there should be a more elegant way to get a callback when a gesture touches a new UIView. Does a functionality like this exist?

Answer 1

I was able to find a more elegant way by using hitTest, which returns the lowest subview with user interaction enabled. I defined the callback for the pan gesture recognizer as such:

var panSelected = Set<UILabel>()
@objc func handlePan(recognizer: UIPanGestureRecognizer) {
    let view = recognizer.view
    let loc = recognizer.location(in: view)
    if let gridLabel = view?.hitTest(loc, with: nil) as? UILabel {
        if !panSelected.contains(gridLabel) {
            // my code here
        }
    }