Objective-C - 多个对象之间的内存管理

多个对象之间的内存管理

/*
 1.你想使用（占用）某个对象，就应该让对象的计数器+1（让对象做一次retain操作）
 2.你不想再使用（占用）某个对象，就应该让对象的计数器-1（让对象做一次release）

 3.谁retain，谁release

 4.谁alloc，谁release
 */

#import <Foundation/Foundation.h>
#import "Person.h"
#import "Book.h"

int main()
{
    // b-1
    Book *b = [[Book alloc] init];
    // p-1
    Person *p1 = [[Person alloc] init];

    //p1想占用b这本书
    // b-2
    [p1 setBook:b];

    // p-0
    // b-1
    [p1 release];
    p1 = nil;

    // b-0
    [b release];
    b = nil;
    return 0;
}

@interface Book : NSObject
{
    int _price;
}

- (void)setPrice:(int)price;
- (int)price;

@end

#import "Book.h"

@implementation Book

- (void)setPrice:(int)price
{
    _price = price;
}

- (int)price
{
    return _price;
}
- (void)dealloc
{
    NSLog(@"Book对象被回收");
    [super dealloc];
}
@end

#import "Book.h"

@interface Person : NSObject
{
    Book *_book;
}

- (void)setBook:(Book *)book;
- (Book *)book;

@end

#import "Person.h"

@implementation Person
- (void)setBook:(Book *)book
{
    _book = [book retain];
}

- (Book *)book
{
    return _book;
}

- (void)dealloc
{
    [_book release];
    NSLog(@"Person对象被回收");
    [super dealloc];
}
@end

set方法的内存管理

 //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];
}

#import "Car.h"

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

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

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

@end

@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

@interface Car : NSObject
{
    int _speed;
}

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

@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 "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

@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

@interface Dog : NSObject

@end

@implementation Dog

@end