Inheritance and Categories

Inherit application: There are several classes when they have some common properties, they can declare a parent class, inherit it. Simplify the code.

Category:

1, which can be used to write code in chunks.

2, expand some system classes. Super powerful.

3, some common methods can be extracted into the nsobject category, because all classes inherit from NSObject, so all classes will have this method, can simplify the code. Generic, add a category to the parent class, and there will be methods in the category in all subclasses.

Common denominator: All can simplify the code. Categories can be added as inheritance.

Inheritance and Categories