OC MRC之循环引用问题（代码分析）

  1 //
  2 //  main.m
  3 //  07-循环引用
  4 //
  5 //  Created by apple on 13-8-9.
  6 //  Copyright (c) 2013年 itcast. All rights reserved.
  7 //
  8 
  9 
 10 /*
 11  1.@class的作用：仅仅告诉编译器，某个名称是一个类
 12  @class Person; // 仅仅告诉编译器，Person是一个类
 13  
 14  2.开发中引用一个类的规范
 15  1> 在.h文件中用@class来声明类
 16  2> 在.m文件中用#import来包含类的所有东西
 17  
 18  3.两端循环引用解决方案
 19  1> 一端用retain
 20  2> 一端用assign
 21  
 22  */
 23 
 24 
 25 #import <Foundation/Foundation.h>
 26 #import "Card.h"
 27 // @class仅仅是告诉编译器，Card是一个类
 28 //@class Card;
 29 
 30 @interface Person : NSObject
 31 
 32 @property (nonatomic, retain) Card *card;
 33 
 34 @end
 35 
 36 #import "Person.h"
 37 #import "Card.h"
 38 
 39 @implementation Person
 40 
 41 - (void)dealloc
 42 {
 43     NSLog(@"Person被销毁了");
 44     [_card release];
 45     
 46     [super dealloc];
 47 }
 48 
 49 @end
 50 
 51 #import <Foundation/Foundation.h>
 52 
 53 @class Person;
 54 
 55 @interface Card : NSObject
 56 
 57 @property (nonatomic, assign) Person *person;
 58 
 59 @end
 60 
 61 #import "Card.h"
 62 #import "Person.h"
 63 
 64 @implementation Card
 65 
 66 
 67 - (void)dealloc
 68 {
 69     NSLog(@"Car被销毁了");
 70     
 71     // [_person release];
 72     
 73     [super dealloc];
 74 }
 75 
 76 @end
 77 
 78 
 79 
 80 #import <Foundation/Foundation.h>
 81 #import "Card.h"
 82 #import "Person.h"
 83 
 84 int main()
 85 {
 86     // p - 1
 87     Person *p = [[Person alloc] init];
 88     // c - 1
 89     Card *c = [[Card alloc] init];
 90     
 91     // c - 2
 92     p.card = c;
 93     
 94     // p - 1
 95     c.person = p;
 96     
 97     // c - 1
 98     [c release];
 99     
100     // p - 0  c - 0
101     [p release];
102     return 0;
103 }