OC MRC之set方法内存管理（代码分析）

 //
 //  main.m
 //  03-set方法的内存管理
 //
 //  Created by apple on 13-8-9.
 //  Copyright (c) 2013年 itcast. All rights reserved.
 //

 #import <Foundation/Foundation.h>

 @interface Dog : NSObject

 @end

 #import "Dog.h"

 @implementation Dog

 @end

 #import <Foundation/Foundation.h>

 @interface Car : NSObject
 {
     int _speed;
 }

 - (void)setSpeed:(int)speed;
 - (int)speed;
 @end

 #import "Car.h"

 @implementation Car
 - (void)setSpeed:(int)speed
 {
     _speed = speed;
 }
 - (int)speed
 {
     return _speed;
 }

 - (void)dealloc
 {
     /*
      _speed ：直接访问成员变量
      self->_speed ：直接访问成员变量
      self.speed : get方法
      [self speed] : get方法
      */

     NSLog(@"速度为%d的Car对象被回收了", _speed);

     [super dealloc];
 }
 @end

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

 @interface Person : NSObject
 {
     Car *_car;
     int _age;
 }

 - (void)setAge:(int)age;
 - (int)age;

 - (void)setCar:(Car *)car;
 - (Car *)car;

 @end

 #import "Person.h"

 // _car -> c1  0

 @implementation Person
 - (void)setCar:(Car *)car
 {
     if (car != _car)
     {
         // 对当前正在使用的车（旧车）做一次release
         [_car release];

         // 对新车做一次retain操作
         _car = [car retain];
     }
 }
 - (Car *)car
 {
     return _car;
 }

 - (void)setAge:(int)age
 { // 基本数据类型不需要管理内存
     _age = age;
 }
 - (int)age
 {
     return _age;
 }

 - (void)dealloc
 {
     // 当人不在了，代表不用车了
     // 对车做一次release操作
     [_car release];

     NSLog(@"%d岁的Person对象被回收了", _age);

     [super dealloc];
 }

 @end

 #import <Foundation/Foundation.h>
 #import "Car.h"
 #import "Dog.h"

 @interface Student : NSObject
 {
     int _no;
     NSString *_name;
     Car *_car;
     Dog *_dog;
 }

 - (void)setNo:(int)no;
 - (int)no;

 - (void)setName:(NSString *)name;
 - (NSString *)name;

 - (void)setCar:(Car *)car;
 - (Car *)car;

 - (void)setDog:(Dog *)dog;
 - (Dog *)dog;

 @end

 #import "Student.h"

 @implementation Student
 - (void)setNo:(int)no
 {
     _no = no;
 }
 - (int)no
 {
     return _no;
 }

 - (void)setName:(NSString *)name
 {
     if ( name != _name )
     {
         [_name release];
         _name = [name retain];
     }
 }

 - (NSString *)name
 {
     return _name;
 }

 - (void)setCar:(Car *)car
 {
     if ( car != _car )
     {
         [_car release];
         _car = [car retain];
     }
 }
 - (Car *)car
 {
     return _car;
 }

 - (void)setDog:(Dog *)dog
 {
     if ( dog != _dog )
     {
         [_dog release];
         _dog = [dog retain];
     }
 }
 - (Dog *)dog
 {
     return _dog;
 }

 - (void)dealloc
 {
     [_name release];
     [_car release];
     [_dog release];

     [super dealloc];
 }
 @end

 #import <Foundation/Foundation.h>
 #import "Car.h"
 #import "Person.h"
 #import "Student.h"
 #import "Dog.h"
 /*
  内存管理代码规范：
  1.只要调用了alloc，必须有release（autorelease）
    对象不是通过alloc产生的，就不需要release

  2.set方法的代码规范
  1> 基本数据类型：直接复制
  - (void)setAge:(int)age
  {
     _age = age;
  }

  2> OC对象类型
  - (void)setCar:(Car *)car
  {
     // 1.先判断是不是新传进来对象
     if ( car != _car )
     {
         // 2.对旧对象做一次release
         [_car release];

         // 3.对新对象做一次retain
         _car = [car retain];
     }
  }

  3.dealloc方法的代码规范
  1> 一定要[super dealloc]，而且放到最后面
  2> 对self（当前）所拥有的其他对象做一次release
  - (void)dealloc
  {
     [_car release];
     [super dealloc];
  }
  */

 // 速度为100的车子：
 // 速度为200的车子：p1->_car

 int main()
 {
     // stu - 1
     Student *stu = [[Student alloc] init];

     // Car - 2
     // 这行内存有内存泄露
     //stu.car = [[Car alloc] init];

     // stu - 0
     // Car - 1
     [stu release];

     // 这行内存有内存泄露
     // [[Car alloc] init].speed = 100;

     return ;
 }

 void test3()
 {
     Student *stu = [[Student alloc] init];

     Car *c = [[Car alloc] init];
     stu.car = c;

     Dog *d = [[Dog alloc] init];

     stu.dog = d;

     NSString *s = @"Jack";

     stu.name = s;

     [d release];
     [c release];
     [stu release];
 }

 void test2()
 {
     Person *p1 = [[Person alloc] init];
     p1.age = ;

     // c1 - 1
     Car *c1 = [[Car alloc] init];
     c1.speed = ;
     // c1 - 2
     p1.car = c1;
     // c1 - 1
     [c1 release];

     Car *c2 = [[Car alloc] init];
     c2.speed = ;
     // c1 - 0
     p1.car = c2;

     [c2 release];

     [p1 release];
 }

 void test1()
 {
     // p-1
     Person *p = [[Person alloc] init];
     p.age = ;

     // c1-1
     Car *c1 = [[Car alloc] init];
     c1.speed = ;

     // c1-2
     p.car = c1;

     // c1-1
     [c1 release];

     p.car = c1;
     p.car = c1;
     p.car = c1;
     p.car = c1;
     p.car = c1;
     p.car = c1;
     p.car = c1;

     [p release];
 }

 void test()
 {
     // p-1
     Person *p = [[Person alloc] init];
     p.age = ;

     // c1-1
     Car *c1 = [[Car alloc] init];
     c1.speed = ;

     // p想拥有c1
     // c1-2
     p.car = c1;  // [p setCar:c1];

     // c2-1
     Car *c2 = [[Car alloc] init];
     c2.speed = ;

     // p将车换成了c2
     // c1-1
     // c2-2
     p.car = c2;

     // c2-1
     [c2 release];
     // c1-0
     [c1 release];
     // p-0 c2-0
     [p release];
 }