OC系列高级－内存管理二

Posted 2020-07-31

一.MRC模式下set和get方法

首先我们创建一个Dog类

Dog.h:

#import <Foundation/Foundation.h>

@interface Dog : NSObject
@property (assign) int ID;
@end

Dog.m:

#import "Dog.h"

@implementation Dog
@synthesize ID = _ID;
- (void)dealloc{
    NSLog(@"Dog ID%d is death",_ID);
    [super dealloc];
}

@end

再创建一饿Person类

Person.h:

#import <Foundation/Foundation.h>
#import "Dog.h"
@interface Person : NSObject
{
    Dog *_dog;
}
-(void)setDog:(Dog *)newDog;
-(Dog *)dog;
@end

Person.m:

#import "Person.h"

@implementation Person

-(void)setDog:(Dog *)newDog{
    NSLog(@"%d",_dog.retainCount);
    if(_dog != newDog){
        [_dog release];
        _dog = nil;
        NSLog(@"%d",_dog.retainCount);
        _dog = [newDog retain];
        NSLog(@"%d",_dog.retainCount);
    }
}

-(Dog *)dog{
    return [_dog autorelease];
}

- (void)dealloc
{
    NSLog(@"Person is death");
    [super dealloc];
}

@end

在main函数中我们创建两个dog,并且创建person

        Dog *dog1 = [[Dog alloc]init];
        dog1.ID = 1;
        Dog *dog2 = [[Dog alloc]init];
        dog2.ID = 2;
        
        Person *p = [[Person alloc]init];

person set一个dog

   [p setDog:dog1];

此时，set方法完之后dog.retainCount值为2，因为dog创建和retain

当我们把dog1 release操作

        [dog1 release];
        NSLog(@"%d",dog1.retainCount);  //值为1

NSLog(@"%zd",p.retainCount);  //person的retainCount值为1，因为只是创建

我们把person release操作

        [p release];
        p = nil;

此时person retainCount值为0,并且调用了dealloc方法,但是person里的dog的retainCount值为1;所以我们在回收person时要把它的对象属性release操作,要不会引起内存空间的泄漏

当person没有执行release操作，再set一个dog1操作，此时，person的dog的retainCount值为1，即没有进行retain操作

注意点：

1.析构函数的release时一定要release掉包含的对象