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I'm trying to detect a double tap with RxSwift

Without RxSwift I would something like this: 

private func setupFakePanView() {
    let singleTapGesture = UITapGestureRecognizer()
    let doubleTapGesture = UITapGestureRecognizer()

    singleTapGesture.numberOfTapsRequired = 1
    doubleTapGesture.numberOfTapsRequired = 2

    singleTapGesture.addTarget(self, action: #selector(self.tapped))
    doubleTapGesture.addTarget(self, action: #selector(self.doubleTapped))

    someView.addGestureRecognizer(singleTapGesture)
    someView.addGestureRecognizer(doubleTapGesture)

    singleTapGesture.require(toFail: doubleTapGesture)
}

@objc private func tapped() {
    // Do something
}

@objc private func doubleTapped() {
    // Do something else
}

Is there a way I could achieve the same with RxSwift, RxCocoa and RxGesture? I've tried the following but of course it doesn't work:

someView.rx
    .tapGesture(numberOfTouchesRequired: 1, numberOfTapsRequired: 1)
    .when(.recognized)
    .subscribe(onNext: { _ in
        // Do something
    })
    .disposed(by: bag)

someView.rx
    .tapGesture(numberOfTouchesRequired: 1, numberOfTapsRequired: 2)
    .when(.recognized)
    .subscribe(onNext: { _ in
        // Do something else
    })
    .disposed(by: bag)

Is there way to let the first tapGesture know the second has to fail?

Tieme
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2 Answers2

3

I've found 2 solutions to solve this problem!

A. Using a custom UITapGestureRecognizer

let doubleTapGesture = UITapGestureRecognizer()
doubleTapGesture.numberOfTapsRequired = 2

let singleTapGesture = UITapGestureRecognizer()
singleTapGesture.numberOfTapsRequired = 1
singleTapGesture.require(toFail: doubleTapGesture)

let singleTap = someView.rx
    .gesture(singleTapGesture)
    .when(.recognized)
    .subscribe(onNext: { _ in
        // Do something
    })
    .disposed(by: bag)


let doubleTap = someView.rx
    .gesture(doubleTapGesture)
    .when(.recognized)
    .subscribe(onNext: { _ in
        // Do something else
    })
    .disposed(by: bag)

or..

B. Using a custom UIGestureRecognizerDelegate

Thanks Kishan for suggesting Jegnux's answer!

1 - Set a custom delegate for the single tap gesture...

someView.rx
    .tapGesture(
        numberOfTouchesRequired: 1,
        numberOfTapsRequired: 1,
        configuration: { [weak self] gesture, delegate in
            gesture.delegate = self
        }
    )
    .subscribe(onNext: { _ in
        // Do something
    })
    .disposed(by: bag)

// double tap same as before

2 - Implement gestureRecognizer(_:shouldRequireFailureOf:)

extension MyController: UIGestureRecognizerDelegate {
    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRequireFailureOf otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        if let gesture = otherGestureRecognizer as? UITapGestureRecognizer, gesture.numberOfTapsRequired == 2 {
             return true
        }
        return false
    }
}

Both solutions work fine.

Community
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Tieme
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2

This code should work:

tap
    .flatMapFirst {
        tap
        .takeUntil(tap.startWith(()).debounce(.milliseconds(300), scheduler: MainScheduler.instance))
        .startWith(())
        .reduce(0) { acc, _ in acc + 1 }
    }
    .map { min($0, 2) }

Just use a single gesture recognizer (whose event is called tap) that emits instantly when a tap occurs. The code above the map generalizes this problem to output the number of successive taps within a certain period of each other (300 ms) in this case. The map is simply to ensure that only a 1 or a 2 comes out. Then do whatever conditional logic with it that you please. I tested it with a UIButton successfully.

Adam H.
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