Cocoa programming is object-oriented, which means that an application consists of objects doing their jobs and coordinating with each other to get things done.
An object is the instance of a class. A class defines a set of related properties and methods (which are similar to functions). A class can create one or more instances of itself, and it is these objects that do the work of the application.
There will be some discussion on classes and objects in Chapter 3, but not a lot. This book assumes that you are at least familiar with the basic concepts object-oriented programming, classes, and instances.
In object-oriented programming, one of the principal design patterns is Model-View-Controller ...