UIButton category/subclass drag and drop iPad

I don't know what's the best way to deal with this problem:

I have some draggable buttons in an app that can be moved on top of some targets. If the button is on top of the right target, let's say button1 is on top of target1, the player/user gets a point. I thought the best way to deal with this would be to make a Target class with an "identifier" attribute and a Draggable class with a "targetID" attribute. When the Draggable object is released, I check whether it's on top of the right Target object by comparing their attributes.

It sounds easy but it 开发者_如何转开发hasn't been. I tried first to make Draggable a subclass of UIButton. As you might already know, that is not a good idea since UIButton returns an instance of a different class when [UIButton buttonWithType:] is called, eg. UIButtonTypeRoundedRect is returned. I can't use a category, since what I need is to have an extra attribute and as far a as I know categories can't add attributes to a class, only methods. Composition would make everything very complicated since I would have to "listen" for the button actions from the controller of Draggable. I will choose this alternative, though, if I don't come with a smarter option.

I might be overseeing something very obvious or I might don't know something absolutely basic. In that case, sorry! My iOS knowledge IS very basic.

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UIButton is a kind of UIView, which has a tag property that you can use to mean anything you want. It's an NSInteger, but that should be useable for what you're trying to do.