Make custom view send action message.

I made a custom view where you can drag a small rectangle around a view. My question is, how can I make it able to send an action message to my app controller? As of now, I can't even wire it up in interface builder, so I'm assuming there's something I need to add to my code. I want it to behave like a slider would, where a change can send an action message to my app controller that checks it and handles it.