前言

例如，有一个Person类：
#import
#import “Book.h”
@interface Person : NSObject
@property(nonatomic,retain)NSString *name;
@property(nonatomic,retain)Book *book;
– (void)read;
@end

#import “Person.h”
@implementation Person
– (void)dealloc
{
NSLog(@“人挂了。。。”):
[_name release];
[_book release];
[super dealloc];
– (void)read
{
[_book castZhiShi];
NSLog(@“啊，书真好。。。”);
}
@end

还有一个Book类：
#import
@class Person;
@interface Book : NSObject
@property(nonatomic,retain)NSString *name;
///书的拥有者
@property(nonatomic,retain)Person *owner;
///传播知识的方法
– (void)castZhiShi;
@end

#import “Book.h”
#import “Person.h”
@implem