UITapGestureReconizer error - xcode

Question

I am getting errors with my UITapGestureReconizer like "UITapGestureReconizer undeclared". Because UITapGestureReconizer is inside a concrete class should it not be declared? and how do I fix it... below is where it first shows up in the code.
- (void)loadView {
[super loadView];
// set the tag for the image view
[imageView setTag:ZOOM_VIEW_TAG];
// add gesture recognizers to the image view
UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(handleDoubleTap:)];
[imageView addGestureRecognizer:doubleTap];
[doubleTap release];
UITapGestureRecognizer *twoFingerTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(handleTwoFingerTap:)];
[imageView addGestureRecognizer:twoFingerTap];
[twoFingerTap release];
[doubleTap setNumberOfTapsRequired:2];
[twoFingerTap setNumberOfTouchesRequired:2];
// calculate minimum scale to perfectly fit image width, and begin at that scale
float minimumScale = [imageScrollView frame].size.width / [imageView frame].size.width;
[imageScrollView setMinimumZoomScale:minimumScale];
[imageScrollView setZoomScale:minimumScale];
}

Answer 1

UITapGestureRecognizer is a part of UIKit, so it should be declared as long as you’re importing <UIKit/UIKit.h> somewhere. One problem I see in your code, though, is this:
UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(handleDoubleTap:)];
[imageView addGestureRecognizer:doubleTap];
[doubleTap release];
…
[doubleTap setNumberOfTapsRequired:2];
At the point where you call [doubleTap setNumberOfTapsRequired:2], you don’t have a valid reference to doubleTap. It’s most likely retained by imageView, but that’s an implementation detail that you can’t rely on. Move the call to -setNumberOfTapsRequired: before the call to -release to ensure that this doesn’t break in a future version of iOS.