OC MRC之循环引用问题（代码分析）

 //
 //  main.m
 //  07-循环引用
 //
 //  Created by apple on 13-8-9.
 //  Copyright (c) 2013年 itcast. All rights reserved.
 //

 /*
  1.@class的作用：仅仅告诉编译器，某个名称是一个类
  @class Person; // 仅仅告诉编译器，Person是一个类

  2.开发中引用一个类的规范
  1> 在.h文件中用@class来声明类
  2> 在.m文件中用#import来包含类的所有东西

  3.两端循环引用解决方案
  1> 一端用retain
  2> 一端用assign

  */

 #import <Foundation/Foundation.h>
 #import "Card.h"
 // @class仅仅是告诉编译器，Card是一个类
 //@class Card;

 @interface Person : NSObject

 @property (nonatomic, retain) Card *card;

 @end

 #import "Person.h"
 #import "Card.h"

 @implementation Person

 - (void)dealloc
 {
     NSLog(@"Person被销毁了");
     [_card release];

     [super dealloc];
 }

 @end

 #import <Foundation/Foundation.h>

 @class Person;

 @interface Card : NSObject

 @property (nonatomic, assign) Person *person;

 @end

 #import "Card.h"
 #import "Person.h"

 @implementation Card

 - (void)dealloc
 {
     NSLog(@"Car被销毁了");

     // [_person release];

     [super dealloc];
 }

 @end

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

 int main()
 {
     // p - 1
     Person *p = [[Person alloc] init];
     // c - 1
     Card *c = [[Card alloc] init];

     // c - 2
     p.card = c;

     // p - 1
     c.person = p;

     // c - 1
     [c release];

     // p - 0  c - 0
     [p release];
     return ;
 }