1. //  Person.h
   
2. #import <Foundation/Foundation.h>
   
3. 
   
4. @class Dog , Card; //@class关键字提前声明两个类，提高性能
   
5. 
   
6. @interface Person : NSObject
   
7. 
   
8. @property(nonatomic , retain) Dog *dog;
   
9. @property(nonatomic , retain) Card *card;
   
10. 
    
11. @end

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1. //  Person.m
   
2. #import "Person.h"
   
3. #import "Dog.h" //.m文件中正式import头文件
   
4. #import "Card.h"
   
5. 
   
6. @implementation Person
   
7. 
   
8. - (void)dealloc
   
9. {
   
10.     NSLog(@"Person被回收");
    
11.     [_dog release]; //retain修饰的属性要进行release操作
    
12.     [_card release];
    
13.     [super dealloc];
    
14. }
    
15. 
    
16. @end

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1. //  Dog.h
   
2. #import <Foundation/Foundation.h>
   
3. #import "Person.h"
   
4. 
   
5. @class Person;
   
6. 
   
7. @interface Dog : NSObject
   
8. 
   
9. @property(nonatomic , assign) Person *owner;
   
10. 
    
11. @end

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1. //  Dog.m
   
2. #import "Dog.h"
   
3. #import "Person.h"
   
4. 
   
5. @implementation Dog
   
6. 
   
7. - (void)dealloc
   
8. {
   
9.     NSLog(@"Dog被回收"); //assign修饰的_owner不需要进行release操作
   
10.     [super dealloc];
    
11. }
    
12. 
    
13. @end

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1. //  Card.h
   
2. #import <Foundation/Foundation.h>
   
3. #import "Person.h"
   
4. 
   
5. @class Person;
   
6. 
   
7. @interface Card : NSObject
   
8. 
   
9. @property(nonatomic , assign) Person *owner;
   
10. 
    
11. @end
    

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1. //  Card.m
   
2. #import "Card.h"
   
3. #import "Person.h"
   
4. 
   
5. @implementation Card
   
6. 
   
7. - (void)dealloc
   
8. {
   
9.     NSLog(@"Card被回收"); //assign修饰的_owner不需要进行release操作
   
10.     [super dealloc];
    
11. }
    
12. 
    
13. @end

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1. //  main.m
   
2. #import <Foundation/Foundation.h>
   
3. #import "Dog.h"
   
4. #import "Card.h"
   
5. #import "Person.h"
   
6. 
   
7. /*
   
8. 类的循环引用：你中有我，我中有你
   
9. * 要使用@class在.h文件中提前声明所应用的类，然后在.m中#import头文件
   
10. *解决办法：一端用retain，另一端用assign
    
11. */
    
12. 
    
13. int main(int argc, const char * argv[])
    
14. {
    
15.     Person *p1 = [[Person alloc] init];
    
16.     Person *p2 = [[Person alloc] init];
    
17.    
    
18.     Dog *d1 = [[Dog alloc] init];
    
19.     Dog *d2 = [[Dog alloc] init];
    
20.    
    
21.     Card *c1 = [[Card alloc] init];
    
22.     Card *c2 = [[Card alloc] init];
    
23.    
    
24.     p1.dog = d1;
    
25.     d1.owner = p1;
    
26.     p1.card = c1;
    
27.     c1.owner = p1;
    
28.    
    
29.     p2.dog = d2;
    
30.     d2.owner = p2;
    
31.     p2.card = c2;
    
32.     c2.owner = p2;
    
33.    
    
34.     //两个人交换dog 和 card
    
35.     p1.dog = d2;
    
36.     d2.owner = p1;
    
37.     p1.card = c2;
    
38.     c2.owner = p1;
    
39.    
    
40.     p2.dog = d1;
    
41.     d1.owner = p2;
    
42.     p2.card = c1;
    
43.     c1.owner = p2;
    
44.    
    
45.     [p1 release];
    
46.     [p2 release];
    
47.     [d1 release];
    
48.     [d2 release];
    
49.     [c1 release];
    
50.     [c2 release];
    
51.    
    
52.     return 0;
    
53. }

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1. //  Person.h
   
2. #import <Foundation/Foundation.h>
   
3. 
   
4. @class Dog , Card; //@class关键字提前声明两个类，提高性能
   
5. 
   
6. @interface Person : NSObject
   
7. 
   
8. @property(nonatomic , retain) Dog *dog;
   
9. @property(nonatomic , retain) Card *card;
   
10. 
    
11. @end

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1. //  Person.m
   
2. #import "Person.h"
   
3. #import "Dog.h" //.m文件中正式import头文件
   
4. #import "Card.h"
   
5. 
   
6. @implementation Person
   
7. 
   
8. - (void)dealloc
   
9. {
   
10.     NSLog(@"Person被回收");
    
11.     [_dog release]; //retain修饰的属性要进行release操作
    
12.     [_card release];
    
13.     [super dealloc];
    
14. }
    
15. 
    
16. @end

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1. //  Dog.h
   
2. #import <Foundation/Foundation.h>
   
3. #import "Person.h"
   
4. 
   
5. @class Person;
   
6. 
   
7. @interface Dog : NSObject
   
8. 
   
9. @property(nonatomic , assign) Person *owner;
   
10. 
    
11. @end

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1. //  Dog.m
   
2. #import "Dog.h"
   
3. #import "Person.h"
   
4. 
   
5. @implementation Dog
   
6. 
   
7. - (void)dealloc
   
8. {
   
9.     NSLog(@"Dog被回收"); //assign修饰的_owner不需要进行release操作
   
10.     [super dealloc];
    
11. }
    
12. 
    
13. @end

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1. //  Card.h
   
2. #import <Foundation/Foundation.h>
   
3. #import "Person.h"
   
4. 
   
5. @class Person;
   
6. 
   
7. @interface Card : NSObject
   
8. 
   
9. @property(nonatomic , assign) Person *owner;
   
10. 
    
11. @end
    

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1. //  Card.m
   
2. #import "Card.h"
   
3. #import "Person.h"
   
4. 
   
5. @implementation Card
   
6. 
   
7. - (void)dealloc
   
8. {
   
9.     NSLog(@"Card被回收"); //assign修饰的_owner不需要进行release操作
   
10.     [super dealloc];
    
11. }
    
12. 
    
13. @end

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1. //  main.m
   
2. #import <Foundation/Foundation.h>
   
3. #import "Dog.h"
   
4. #import "Card.h"
   
5. #import "Person.h"
   
6. 
   
7. /*
   
8. 类的循环引用：你中有我，我中有你
   
9. * 要使用@class在.h文件中提前声明所应用的类，然后在.m中#import头文件
   
10. *解决办法：一端用retain，另一端用assign
    
11. */
    
12. 
    
13. int main(int argc, const char * argv[])
    
14. {
    
15.     Person *p1 = [[Person alloc] init];
    
16.     Person *p2 = [[Person alloc] init];
    
17.    
    
18.     Dog *d1 = [[Dog alloc] init];
    
19.     Dog *d2 = [[Dog alloc] init];
    
20.    
    
21.     Card *c1 = [[Card alloc] init];
    
22.     Card *c2 = [[Card alloc] init];
    
23.    
    
24.     p1.dog = d1;
    
25.     d1.owner = p1;
    
26.     p1.card = c1;
    
27.     c1.owner = p1;
    
28.    
    
29.     p2.dog = d2;
    
30.     d2.owner = p2;
    
31.     p2.card = c2;
    
32.     c2.owner = p2;
    
33.    
    
34.     //两个人交换dog 和 card
    
35.     p1.dog = d2;
    
36.     d2.owner = p1;
    
37.     p1.card = c2;
    
38.     c2.owner = p1;
    
39.    
    
40.     p2.dog = d1;
    
41.     d1.owner = p2;
    
42.     p2.card = c1;
    
43.     c1.owner = p2;
    
44.    
    
45.     [p1 release];
    
46.     [p2 release];
    
47.     [d1 release];
    
48.     [d2 release];
    
49.     [c1 release];
    
50.     [c2 release];
    
51.    
    
52.     return 0;
    
53. }

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