Objective-c – convertPoint:

I was struggling with this same problem - I was trying to do a interface with a lot of "cards" (UIView subclasses) on a cork board, and have the cork board area scrollable, but still able to drag-and-drop the cards. I was doing the hitTest() solution above, but one of the Apple engineers asked me why I was doing it that way. The simpler solution they suggested was as follows:

1) In the UIScrollView class, set the value of canCancelContentTouches to NO - this tells the UIScrollView class to allow touches within subviews (or, in this case, in subviews of subviews).

2) In my "card" class, set exclusiveTouch to YES - this tells the subview it owns the touches inside of it.

After this, I was able to drag around the cards and still scroll the subview. It's a lot simpler and cleaner than the hitTest() solution above.

(BTW, for extra credit, if you are using iOS 3.2 or 4.0 or later, use the UIPanGestureRecognizer class to handle the drag and drop logic - the drag and drop motion is a lot smoother than overriding touchesBegan()/touchesMoved()/touchesEnded().)

The usual cause of something like this is over releasing objects. If you run your code with NSZombieEnabled, the console output should give you a clue as to where to look.

Alternatively, if this is a Macintosh application targeted at 10.5 or greater, you can enable garbage collection and not worry about retain and release at all.