Reconhecedor de gestos e ações do botão

Eu tenho uma hierarquia de exibição que se parece com isso:

UIView (A)
UIView > UIImageView
UIView > UIView (B)
UIView > UIView (B) > Rounded Rect Button
UIView > UIView (B) > UIImageView
UIView > UIView (B) > UILabel

Anexei reconhecedores de gestos ao meu UIView (B). O problema que estou enfrentando é que não recebo nenhuma ação para o botão Retângulo Arredondado que está dentro do UIView (B). O reconhecedor de gestos singleTap captura / substitui o evento Touch Up Inside do botão.

Como posso fazer funcionar? Eu pensei que a hierarquia da cadeia de resposta garantiria que o evento de toque no botão tenha preferência e será acionado! O que estou perdendo?

Aqui está um código relacionado:

#pragma mark -
#pragma mark View lifecycle (Gesture recognizer setup)

- (void)viewDidLoad {
    [super viewDidLoad];

    // double tap gesture recognizer
    UITapGestureRecognizer *dtapGestureRecognize = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(doubleTapGestureRecognizer:)];
    dtapGestureRecognize.delegate = self;
    dtapGestureRecognize.numberOfTapsRequired = 2;
    [self.viewB addGestureRecognizer:dtapGestureRecognize];

    // single tap gesture recognizer
    UITapGestureRecognizer *tapGestureRecognize = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(singleTapGestureRecognizer:)];
    tapGestureRecognize.delegate = self;
    tapGestureRecognize.numberOfTapsRequired = 1;
    [tapGestureRecognize requireGestureRecognizerToFail:dtapGestureRecognize];
    [self.viewB addGestureRecognizer:tapGestureRecognize];

    // add gesture recodgnizer to the grid view to start the edit mode
    UILongPressGestureRecognizer *pahGestureRecognizer = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPressGestureRecognizerStateChanged:)];
    pahGestureRecognizer.delegate = self;
    pahGestureRecognizer.minimumPressDuration = 0.5;
    [self.viewB addGestureRecognizer:pahGestureRecognizer];

    [dtapGestureRecognize release];
    [tapGestureRecognize release];
    [pahGestureRecognizer release];
}

#pragma mark -
#pragma mark Button actions

- (IBAction)buttonTouchUpInside:(id)sender {
    NSLog(@"%s, %@", __FUNCTION__, sender);
}

#pragma mark -
#pragma mark Gesture recognizer actions


- (void)singleTapGestureRecognizer:(UIGestureRecognizer *)gestureRecognizer {
    NSLog(@"%s", __FUNCTION__);
}

- (void)doubleTapGestureRecognizer:(UIGestureRecognizer *)gestureRecognizer {
    NSLog(@"%s", __FUNCTION__);
}

- (void)longPressGestureRecognizerStateChanged:(UIGestureRecognizer *)gestureRecognizer {

    switch (gestureRecognizer.state) {

        case UIGestureRecognizerStateEnded: {
            NSLog(@"%s", __FUNCTION__);

            break;
        }
        default:
            break;
    }
}

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