IOS uses categories category and extension extension

In OC, the classes in the library can be extended on an original basis.

For example, to add new attribute variables and methods to nssting, you can create a new. m file in Xcode

Select the corresponding original class

Then you can select the extension or classification, the classification will be automatically connected with the + number, the extension will automatically connect with _, such as

"Nsstring+security.h"

"Nsstring_extension.h"

The extension can add attribute variables and methods, but only adds a new header file

Categories can add methods, cannot add attribute variables, have a header file and a. m file, and M files can implement specific methods

So in the classification of reference to the extension of the header file, you can do a method of a class of property variables to add, and in the M file can be implemented in specific ways

IOS uses categories category and extension extension