iOS Development categories, extensions

Category:

In iOS project development, it is possible to use categories to add new methods to existing classes, and you do not need to create subclasses. By category we can dynamically add new methods to existing classes, and you can modularize the definition of a class into multiple related files.

The benefits of using categories are:

First, the modular design

Ii. use of categories to invoke private methods

The interface section is formatted as follows:

@interface already have Class (category name)

Definition of a method

.....

@end

Note: Typically only new methods are defined in a category.

The syntax format for the implementation section of the category is as follows:

@implmentation already have Class (category name)

Implementation of the method

@end

I'll start by creating an old class

Then chuangjian a new category, such as

The methods are created in the old class and the new class, and finally in the MAIN.M function call method:

Extended

Extensions are similar to categories, with extensions equivalent to anonymous categories, in the following format:

@interface already have a class ()

Definition of a method

.....

@end

The difference between a category and an extension is:

Categories generally do not re-increment variables, only add new methods, and extensions can.

Extension only the interface file (. h) Without implementing the method defined by the file (. m) is implemented inside the class

iOS Development categories, extensions