8. Inheritance

In this chapter, you learn about one of the key principles that makes object-oriented programming so powerful. Through the concept of inheritance, you build on existing class definitions and customize them for your own applications.

It All Begins at the Root

You learned about the idea of a parent class in Chapter 3, “Classes, Objects, and Methods.” A parent class can itself have a parent. The class that has no parent is at the top of the hierarchy and is known as a root class. In Objective-C, you can define your own root class, but it’s something you normally won’t want to do. Instead, you want to take advantage of existing classes. All the classes we’ve defined up to this point are descendants of the root class called NSObject ...

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