Categories and extensions of iOS development

Categories and extensions of iOS development
Category:

In ios project development, you can use a category to add a new method to an existing class without creating a subclass. By using categories, we can dynamically add new methods to existing classes and modularize the definition of classes to multiple related files.

Benefits of using categories:

I. Modular Design

Ii. Use category to call private methods

The Interface format is as follows:

@ Interface existing class (category name)

// Method definition

.....

@ End

Note: Only new methods are defined in a category.

The syntax format of category implementation is as follows:

@ Implmentation existing class (category name)

// Method implementation

@ End

Create an old class first

Then a new category, such

Methods are created in the old class and new class respectively, and finally the method for calling the main. m function is as follows:

 

Extension

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

 

@ Interface existing class ()

// Method definition

.....

@ End

The difference between category and extension is:

Classes generally do not add variables again. They only add new methods, but can be extended.

The extension is only implemented in the interface file (. h) but not the method defined in the file (. m ).