iOS categories and extensions-Chaoxiaopo

Category

@interface ClassName (CategoryName)
Methoddeclarations
@end

category is used very frequently in iOS development . < Span style= "color: #ff0000;" In particular, when it comes to extending the system classes, we can add methods to the system classes without inheriting the system classes, maximizing the dynamic language characteristics of objective-c .

Precautions

1: A category is an extension of a class , only methods can be declared, and variables cannot be declared. Also, class methods have higher precedence and can override the original class method.

2: The Super method cannot be called in a class method. --The limitations of categories

3: Thecategory method cannot be overridden in other category methods in the same class. Because they do not anticipate their load precedence, they may have errors at compile time.

Use Category:

1. Provides the extension of the class to the framework (no source code, cannot be modified).

2. If you do not want to generate a new subclass, such as an extension to Nsarray.

3. Easy to do project management, can be a source in multiple places to share or do the method version management, multi-person collaborative development, with the local version of the replacement of the public version of the implementation.

Extended:

1: In some cases, we need to declare a @property, which is read-only (ReadOnly) and internally readable (ReadWrite), which can be achieved by extensions

@interfaceBaseclass:nsobject@property (READONLY) NSString *privatestring;@end//. m@interface BaseClass () @property (readwrite) NSString *< Span style= "margin:0px; padding:0px; font-family: ' Courier new '; >privatestring;  @end  @implementation  Baseclass @synthesize  Privatestring;//... @end 
          

2: Enables the editor to better validate private methods or variables of a class

  @interface void @end  @implementation  Baseclass//... @end           

     

iOS categories and extensions-Chaoxiaopo