OC language @property @synthesize and ID

One, @property @synthesize keywords

Note: These two keywords are compiler features that allow Xcode to automatically generate The declarations and implementations of getter and setter.

(i) @property keywords

@property keyword can automatically generate a declaration of the setter and getter method for a member variable

@property int age;

When the compilation encounters this line, it is automatically extended to the following two sentences:

-(void) Setage: (int) age;

-(int) age;

(ii) @synthesize keywords

@synthesize keyword helps generate the implementation of the setter and getter methods for member variables.

Syntax:@synthesize age=_age;

Equivalent to the following code:

- (void)setage: (int) Age

{

_age=age;

}

-(int) age

{

Return _age;

}

(iii) Use and use of keywords note

The declarations section of the class:

The implementation part of the class:

Test procedure:

In the new version:

The declarations section of the class:

The implementation part of the class:

Test procedure:

(1) in old-fashioned code,@property can only be written in @interface @end ,@synthesize can only be written in @implementation @end , since after Xcode 4.4 ,@property @property and @synthesize functions.

(2) @property int age;This sentence is complete.31 ) generate _age get and set" Generate _age member variable set and get3 "Create a _age

Note: The member variables generated in this way are private .

(3) You can add int _age to {}; The declaration shown is _age to protected .

(4) Principle:get and set methods are the same as variables, if you define yourself, then use what you have defined, if not defined, then automatically generate a.

(5) Manual implementation:

1) If the Set method is implemented manually , then the compiler generates only the get methods and member variables;

2) If the Get method is implemented manually , then the compiler generates only the set method and member variable;

3) If both the set and get methods are implemented manually, the compiler will not generate member variables.

Second, Id

An ID is a type, universal pointer that can point to \ manipulate any object.

Note: In the definition of ID, the * number is already wrapped . The Id pointer can only point to an OS object.

definition of ID type

Typedef struct OBJC object{

Class Isa;

} *id;

Limitations: Call a nonexistent method, the compiler will immediately error.

OC language @property @synthesize and ID