Objective-C - 循环引用问题

循环引用问题

/*
 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"
#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 0;
}

#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 "Card.h"

@implementation Person

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

    [super dealloc];
}

@end

@class Person;

@interface Card : NSObject

@property (nonatomic, assign) Person *person;

@end

@implementation Card

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

    // [_person release];

    [super dealloc];
}

@end