SwipeGesture in scrollView: require to fail.

ScrollViewSwipeGestureRequireToFail.swift

class ChildViewController: UIViewController {
	func addSwipeGesture() {
		let leftGestureRecognizer = UISwipeGestureRecognizer(target: self, action: #selector(swipe))
		let rightGestureRecognizer = UISwipeGestureRecognizer(target: self, action: #selector(swipe))
		
		leftGestureRecognizer.delegate = self
		rightGestureRecognizer.delegate = self
		
		leftGestureRecognizer.direction = UISwipeGestureRecognizerDirection.left
		rightGestureRecognizer.direction = UISwipeGestureRecognizerDirection.right
		
		view.addGestureRecognizer(leftGestureRecognizer)
		view.addGestureRecognizer(rightGestureRecognizer)
		
		parentScrollView.panGestureRecognizer.require(toFail: leftGestureRecognizer)
		parentScrollView.panGestureRecognizer.require(toFail: rightGestureRecognizer)
  }
}

extension ChildViewController: UIGestureRecognizerDelegate {
	func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
		// return true/false to enable/disable the left/right gesture 
	}
}