Class extension, class category, Class-continuation category

Class extension

• OBJECTIVE-C 2.0 adds the class extensions to solve two problems:

1. Allows an object to have a private interface and can be validated by the compiler.
2. Supports a public read-only, private writable property.

• Extension is more like an anonymous category.

Class Category

• The category is more likely to be written in a separate file, followed by the name "Nsview+customadditions.h", implemented in block blocks in the corresponding. m file. Therefore, Cagegory is more inclined to separate the functions of class, and to organize the function modules of classes.
• Extension prefers to write at the top of the. m file of the same class, and its implementation is placed in the implementation block of that class.
• such as the last Uiimage+display.h, is the system of the UIImage class supplement

Difference between Category and Class Extension?

• A category is a A-methods to add-to-existing classes. They usually reside in files called "Class+categoryname.h", like "Nsview+customadditions.h" (and. m, of course).
• A class extension is a category, except for 2 main differences:
  • The category has no name. It's declared like this:

  •   @interface   SomeClass () -(void  ) Anadditionalmethod; 
       @end  

• • The implementation of the extension must is in the main @implementation block of the file.
• It ' s quite common to see a class extension at the top of a. m file declaring more methods on the class, that's then Impl Emented below in the main @implementation section of the class. This is a-to-declare "Pseudo-private" methods (pseudo-private in that they ' re isn't really private, just not externally Exposed).

Class-continuation category

Class-continuation category See "Effective OBJECTIVE-C 2.0" 27th

Class extension, class category, Class-continuation category