UIPanGestureRecognizer beyondBounds - objective-c

Question

I have this code that retrieves the coordinates of an object when it is panned:
UITapGestureRecognizer *moveBuildingTap = [[UITapGestureRecognizer alloc]
initWithTarget:self action:#selector(moveobject:)];
Method moveobject contents:
CGPoint tapPoint=[recognizer locationOfTouch:0 inView:self.view];
I use this to change the frame of - move it -an imageview using these coordinates.
However, upon dragging the image around - triggering the uipangesturerecognizer action, I found that when I drag it to the absolute bottom, I get an error that -[UIPanGestureRecognizer locationOfTouch:inView:]: index (0) beyond bounds (0).
How can I solve this exception and prevent the user from dragging past this point?
Thanks

Answer 1

It's weird that your moveobject: method gets called even though the private touches array of the gesture recognizer seems to be empty.
Anyway, in general, if you don't handle multitouch gestures within gesture recognizer, I would suggest to use [recognizer locationInView:] rather then locationOfTouch:inView:.
Btw:
Your talking about a UIPanGestureRecognizer while in the code you're using a UITapGestureRecognizer.
The code I would recommend to handle dragging of a particular view looks like this:
//...
UIPanGestureRecognizer *panGR = [[UIPanGestureRecognizer alloc] initWithTarget:self action:#selector(handlePan:)];
[someView addGestureRecognizer:panGR];
//...
- (void)handlePan:(UIPanGestureRecognizer *)gr
{
CGPoint translation = [gr translationInView:gr.view];
gr.view.frame = CGRectOffset(gr.view.frame, translation.x, translation.y);
[gr setTranslation:CGPointZero inView:gr.view];
}

Answer 2

You should check the numberOfTouches in your UIGestureRecognizer like:
if (recognizer.numberOfTouches) {
CGPoint tapPoint = [recognizer locationOfTouch:0 inView:self.view];
}