The first question new Cocoa programmers ask me when they get to this stage is: “How do I send data between classes?” There’s no magic sendDataToClass method or anything like that. Instead, you use Model-View-Controller, or, more commonly, MVC. This isn’t a class—it’s a mindset.
In a nutshell, MVC says that there are three kinds of objects: model objects, which hold raw data; view objects, which the user can see and click on; and controller objects, which keep the model and view objects in sync.