iOS @property properties and @synthesize properties

When you define a series of variables, you need to write a lot of getter and setter methods, and they are all similar in form, so Xcode provides @property and @synthesize attributes, @property used as a declaration in the. h header file, @ Synthesize is used in. m files for implementation.

For example, create a new project based on Command line Tool, called "Property", and then create a new student class, which is traditionally written as:

Student.h

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Student.h
Property
//
Created by rio.king on 13-8-25.
Copyright (c) 2013 rio.king. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface Student:nsobject
{
int age;
int no;
}

Age getter and setter method declaration
-(int) age;
-(void) Setage: (int) newage;

Getter and setter method declaration of No
-(int) No;
-(void) Setno: (int) Newno;

@end
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Student.m

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//
Student.m
Property
//
Created by rio.king on 13-8-25.
Copyright (c) 2013 rio.king. All rights reserved.
//

#import "Student.h"

@implementation Student

Implementation of getter and setter methods for age
-(int) age
{
return age;
}
-(void) Setage: (int) newage
{
age = NewAge;
}

The realization of the getter and setter method of No
-(int) No
{
return no;
}
-(void) Setno: (int) Newno
{
no = Newno;
}

@end
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Main.m

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//
Main.m
Property
//
Created by rio.king on 13-8-25.
Copyright (c) 2013 rio.king. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "Student.h"

int main (int argc, const char * argv[])
{

@autoreleasepool {

Insert code here ...
Student *stu = [[Student alloc] init];
Stu.age = 100;//This sentence is equivalent to setter method
NSLog (@ "Age is%i", stu.age);//The stu.age here is equivalent to the Getter method

[Stu release];

}
return 0;
}
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************************************************************************************



The @property and @synthesize are:
Student.h

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//
Student.h
Property
//
Created by rio.king on 13-8-25.
Copyright (c) 2013 rio.king. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface Student:nsobject
{
int age;
int no;
}

When the compiler encounters @property, the declaration of getter and setter is automatically expanded
@property int age;
@property int No;


@end
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Student.m

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//
Student.m
Property
//
Created by rio.king on 13-8-25.
Copyright (c) 2013 rio.king. All rights reserved.
//

#import "Student.h"

@implementation Student

@synthesize will automatically generate getter and setter implementations
@synthesize the default is to access a variable with the same name as Age,no,height,
If a variable of the same name cannot be found, it automatically generates a private variable age,no,height with the same name internally,
Therefore, these variables in the Student.h can also be omitted and not written.
@synthesize Age,no;

@end
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Main.m

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//
Main.m
Property
//
Created by rio.king on 13-8-25.
Copyright (c) 2013 rio.king. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "Student.h"

int main (int argc, const char * argv[])
{

@autoreleasepool {

Insert code here ...
Student *stu = [[Student alloc] init];
Stu.age = 100;
NSLog (@ "Age is%i", stu.age);

[Stu release];
}
return 0;
}
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A few notes:
1. In Xcode4.5 and later versions, you can omit @synthesize, the compiler will automatically help you add getter and setter method implementation, and the default will be to access the _age member variable, if the _age can not find this member variable, will automatically generate a called _ The private member variable of age.

2. Video teaching suggested variable name with "_" prefix as the beginning, but I see big Nerd the book is not used, the individual is also more accustomed to the big Nerd that way, so the variable name is not prefixed.



Introduction to Syntax:
Format: The syntax for declaring the property is: @property (parameter 1, parameter 2) type name; Such as:
C code
@property (Nonatomic,retain) UIWindow *window;
The parameters are mainly divided into three categories:
Read-Write properties: (readwrite/readonly)
Setter semantics: (assign/retain/copy)
Atomicity: (atomicity/nonatomic)

The meaning of each parameter is as follows:
ReadWrite: Generating Setter\getter methods
ReadOnly: Only produce simple getter, no setter.
Assign: Default type, setter method directly assign value without retain action
Retain:setter method to release the old value of the parameter, and then retain the new value.
Copy:setter method for copy operation, same as retain
Nonatomic: Prohibit multiple threads, variable protection, improve performance