Car.h:

#import <Foundation/Foundation.h>  @interface Card : NSObject  @end

Car.m:

#import "Card.h"  @implementation Card -(void)dealloc{     NSLog(@"Card被销毁");     [super dealloc]; } @end

Book.h:

#import <Foundation/Foundation.h>  @interface Book : NSObject  @end

Book.m:

#import "Book.h"  @implementation Book  -(void)dealloc{     NSLog(@"Book被销毁了"); }  @end

Student.h:

#import <Foundation/Foundation.h> @class Book; @class Card;  @interface Student : NSObject{     Book *_book; } //retain参数相当于.m中的setCard中的一大坨,nonatomic参数相当于set，get方法不需要枷锁，不需要线程保护，提高效率，一般都加nonatomic属性，以提高性能 @property(nonatomic,retain) Book *book; //retain参数相当于.m中的setCard中的一大坨 @property(retain) Card *card; //readonly是具有只读属性 还有readwrite属性 @property(readwrite) int age;  //属性默认就是atomic属性，能够提供给多个线程调用，get和set方法进行枷锁，保证线程安全 @property(atomic) int no; //getter实现了方法名 @property(nonatomic,getter = isRich) BOOL rich; @end

Student.m:

#import "Student.h" #import "Book.h"  @implementation Student //-(void)setBook:(Book *)book{ //    if(_book!=book) //    { //        [_book release]; //         _book=[_book retain]; //         //    } //}  //setCard相当于.h之前@property（retain）参数 自动实现 //-(void)setCard:(Card *)card{ //    if(_card!=card) //    { //        [_card release]; //        _card=[_card retain]; //    } //}  //getf方法可以由系统自动帮助实现 //-(Book *)book{ //    return _book; //} -(void)dealloc{     NSLog(@"Student被销毁");     [_book release];     [_card release];     [super dealloc]; } @end

main:

#import <Foundation/Foundation.h> #import "Student.h" #import "Book.h" #import "Card.h"  int main(int argc, const char * argv[]) {      @autoreleasepool {                  Student *student =[[Student alloc] init];         Book *book=[[Book alloc] init];         student.book=book;         //student.rich=YES;         //BOOL _rich=student.isRich;//前面Student.h中实现了getter方法名                  Card *card=[[Card alloc] init];         [card release];         [book release];         [student release];     }     return 0; }
结果：

2013-08-02 15:03:12.496 内存管理3 @property参数[871:303] Card被销毁

2013-08-02 15:03:12.498 内存管理3 @property参数[871:303] Student被销毁

2013-08-02 15:03:12.499 内存管理3 @property参数[871:303] Book被销毁了