Should superview's gesture cancel subview's gesture in iOS 7?

Question

For several years now I\'ve operated under the assumption that if a superview and its subview both have gesture recognizers, the subview would receive the touches first and

Answer 1

After a lot of searching around I found a discussion on Apple's message boards with other users that are having this problem: Issues with UITapGestureRecognizer (developer account required). I went ahead and submitted a bug report: 15331126 (does anyone know how to link to bug reports anymore?). In the meantime, I implemented this workaround. So far it seems to be working, but since the bug is so rare I may simply not have triggered it yet. I'm releasing it to my beta users and if I get no complaints from them (who have been complaining) I'll assume this fixes the issue.

UPDATE: This solution has fixed the problem. After weeks of use by dozens of users I haven't had a single issue with gestures.

Most of my gestures are custom. I altered them to be delegates of themselves and implemented:

- (BOOL) gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer{
    if (gestureRecognizer == self){
        if ([otherGestureRecognizer isMemberOfClass:self.class]){
            if ([self isGestureRecognizerInSuperviewHierarchy:otherGestureRecognizer]){
                return YES;
            } else if ([self isGestureRecognizerInSiblings:otherGestureRecognizer]){
                return YES;
            }
        }
    }
    return NO;
}

Note that my custom gestureRecognizers implement the UIGestureRecognizerDelegate protocol now (publically, for reasons you'll see below). I also added a couple of categories to UIGestureRecognizer (used in the above code):

- (BOOL) isGestureRecognizerInSiblings:(UIGestureRecognizer *)recognizer{
    UIView *superview = self.view.superview;
    NSUInteger index = [superview.subviews indexOfObject:self.view];
    if (index != NSNotFound){
    for (int i = 0; i < index; i++){
            UIView *sibling = superview.subviews[i];
            for (UIGestureRecognizer *viewRecognizer in sibling.gestureRecognizers){
                if (recognizer == viewRecognizer){
                    return YES;
                }
            }
        }
    }
    return NO;
}
- (BOOL) isGestureRecognizerInSuperviewHierarchy:(UIGestureRecognizer *)recognizer{
    if (!recognizer) return NO;
    if (!self.view) return NO;
    //Check siblings
    UIView *superview = self.view;
    while (YES) {
        superview = superview.superview;
        if (!superview) return NO;
        for (UIGestureRecognizer *viewRecognizer in superview.gestureRecognizers){
            if (recognizer == viewRecognizer){
                return YES;
            }
        }
    }
}

I'm not entirely sure that I need to check for siblings as I've only seen the issue occur with superview gestures. However, I didn't want to take that chance. Note that I only check for siblings "below" the current one as I don't want to cancel view gestures "above" the current view.

I had to add implementations for for those classes that set themselves as delegates of the custom recognizers, but they pretty much just call back to the gestureRecognizer:

- (BOOL) gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer{
    if ([gestureRecognizer respondsToSelector:@selector(gestureRecognizer:shouldBeRequiredToFailByGestureRecognizer:)]){
        return [(id <UIGestureRecognizerDelegate>)gestureRecognizer gestureRecognizer:gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:otherGestureRecognizer];
    }
    return NO;
}

Hope this helps anyone else having the problem.