The Core iOS Developer’s Cookbook, Fifth Edition

Touching Views

When dealing with many onscreen views, iOS automatically decides which view the user touched and passes any touch events to the proper view for you. This helps you write concrete direct manipulation interfaces where users touch, drag, and interact with onscreen objects.

Just because a touch is physically on top of a view doesn’t mean that a view has to respond. Each view can use a “hit test” to choose whether to handle a touch or to let that touch fall through to views beneath it. As you’ll see in the recipes that follow, you can use clever response strategies to decide when your view should respond, particularly when you’re using irregular art with partial transparency.

With touch events, the first view that passes the hit test ...