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 0;
}


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 = 20;
    
    // c1 - 1
    Car *c1 = [[Car alloc] init];
    c1.speed = 100;
    // c1 - 2
    p1.car = c1;
    // c1 - 1
    [c1 release];
    
    Car *c2 = [[Car alloc] init];
    c2.speed = 200;
    // c1 - 0
    p1.car = c2;
    
    [c2 release];
    
    [p1 release];
}

void test1()
{
    // p-1
    Person *p = [[Person alloc] init];
    p.age = 20;
    
    // c1-1
    Car *c1 = [[Car alloc] init];
    c1.speed = 250;
    
    // 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 = 20;
    
    // c1-1
    Car *c1 = [[Car alloc] init];
    c1.speed = 250;
    
    // p想拥有c1
    // c1-2
    p.car = c1;  // [p setCar:c1];
    
    // c2-1
    Car *c2 = [[Car alloc] init];
    c2.speed = 300;
    
    // 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];
}