pragma mark 循环retain

pragma mark 概念

/**
 循环retain 
 你拥有我,我拥有你
 释放的时候没有办法释放成功
 */

pragma mark 代码

#import <Foundation/Foundation.h>
#pragma mark 类
#import "Person.h"
#import "Dog.h"
#pragma mark main函数
int main(int argc, const char * argv[])
{
    Person *p = [Person new];
    Dog *d = [Dog new];
    
    // 如果A对象要拥有B对象,而B对象又要拥有A对象,此时会形成循环retain
#warning 如何解决循环retain
    // 不要让A retain B , B retain A
    // 让其中一方不要retain操作即可
    
    p.dog = d;      // 人 有一条狗    retain
    d.owner = p;    // 狗 有一个主人  assign
    
    
    /*
     Person object 0x1007000a0 overreleased while already deallocating; break on objc_overrelease_during_dealloc_error to debug
     // 野指针错误 开启僵尸对象 edit Scheme -> Run -> diagnostic -> Enable Zombie Objects
     [Person release]: message sent to deallocated instance 0x100605d80
     把release操作交换一下 即可 
     // 如果不交换 可以直接把dog中的dealloc中的 [_owner release]; 注释即可
     [p release];
     [d release];

     */
    
    // 这里会出现过度释放,潜在的隐患
    // 解决办法是 最好在dealloc 里面设置setter方法为nil
    // 在dealloc里面 只要调用setter方法 =nil 怎么写都不会报错 self.owner = nil、self.dog = nil
    
    [d release];
    [p release];
    
    return 0;
}

Person.h //人类

#import <Foundation/Foundation.h>
@class Dog;

@interface Person : NSObject

@property(nonatomic, retain)Dog *dog;

@end

Person.m

#import "Person.h"
#import "Dog.h"

@implementation Person

- (void)dealloc
{
    NSLog(@"%s",__func__);
//    [_dog release];
    self.dog = nil;
    [super dealloc];
    
}
@end

---

Dog.h //狗类

#import <Foundation/Foundation.h>
@class Person;
@interface Dog : NSObject

//@property(nonatomic, retain)Person *owner;
@property(nonatomic, assign)Person *owner;

@end

Dog.m

#import "Dog.h"
#import "Person.h"
@implementation Dog

- (void)dealloc
{
//    [_owner release]; assgin 就不需要release
    self.owner = nil;
    NSLog(@"%s",__func__);
    [super dealloc];
}
@end

---