UISegmentedControl deselect / reset after view disappears

Question

I'm trying to fix a small bug. I have an UISegmentedControl that stays showing user interaction if I navigate back while pressing a segment (without releasing the finger which is selecting the segment from the screen):

I tried to deselect the segment on viewWillDisappear but I doesn't make a difference. Any ideas on how to reset the state of the UISegmentedControl?

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)

    fixedPositionSegmentControl.selectedSegmentIndex = UISegmentedControl.noSegment
    fixedPositionSegmentControl.selectedSegmentIndex = 0
}

Answer 1

The problem is that in this specific case (leaving the screen while touching the control) the segmented control's touchesEnded / touchesCancelled functions do not get called. So you could cancel the touch programmatically:

override func viewDidDisappear(_ animated: Bool) {
    segmentedControl.touchesCancelled(Set<UITouch>(), with: nil)
    super.viewDidDisappear(animated)
}

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    segmentedControl.selectedSegmentIndex = 0
}

Subclassing UISegmentedControl might even be the cleaner (but maybe oversized) approach:

class SegmentedControl: UISegmentedControl {

    // property to store the latest touches
    private var touches: Set<UITouch>?

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesBegan(touches, with: event)
        self.touches = touches
    }

    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesMoved(touches, with: event)
        self.touches = touches
    }

    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesEnded(touches, with: event)
        self.touches = nil
    }

    override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesCancelled(touches, with: event)
        self.touches = nil
    }

    override func didMoveToWindow() {
        // cancel pending touches when the view is removed from the window
        if window == nil, let touches = touches {
            touchesCancelled(touches, with: nil)
        }
    }

}

With that approach you can simply reset the index in viewWillAppear:

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    segmentedControl.selectedSegmentIndex = 0
}