第十六讲：Objective-C内存管理之“黄金法则”

Sian

Person.h

1. //
2. //  Person.h
3. //  memory
4. //
5. //  Created by yusian on 14-1-11.
6. //  Copyright (c) 2014年 yusian. All rights reserved.
7. //
9. #import <Foundation/Foundation.h>
10. #import "Dog.h"
12. @interface Person : NSObject
13. {
14.     Dog * _dog;
15. }
17. - (void) setDog:(Dog *)aDog;
18. - (Dog *) dog;
20. @end

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Person.m

1. //
2. //  Person.m
3. //  memory
4. //
5. //  Created by yusian on 14-1-11.
6. //  Copyright (c) 2014年 yusian. All rights reserved.
7. //
9. #import "Person.h"
11. @implementation Person
13. - (Dog *) dog{
14.     return _dog;
15. }
17. - (void) setDog:(Dog *)aDog{
18.     if (aDog != _dog) {
19.         [_dog release];
20.         _dog = [aDog retain];
21.     }
22. }
24. - (void) dealloc{
25.     NSLog(@"Person is dealloc!");
26.     [_dog release];
27.     [super dealloc];
28. }
30. @end

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Dog.h

1. //
2. //  Dog.h
3. //  memory
4. //
5. //  Created by yusian on 14-1-11.
6. //  Copyright (c) 2014年 yusian. All rights reserved.
7. //
9. #import <Foundation/Foundation.h>
11. @interface Dog : NSObject
12. {
13.     int _ID;
14. }
16. @property int ID;
18. @end

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Dog.m

1. //
2. //  Dog.m
3. //  memory
4. //
5. //  Created by yusian on 14-1-11.
6. //  Copyright (c) 2014年 yusian. All rights reserved.
7. //
9. #import "Dog.h"
11. @implementation Dog
13. @synthesize ID = _ID;
15. - (void) dealloc{
16.     NSLog(@"Dog %d is dealloc!",_ID);
17.     [super dealloc];
18. }
19. @end

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main.m

1. //
2. //  main.m
3. //  memory
4. //
5. //  Created by yusian on 14-1-11.
6. //  Copyright (c) 2014年 yusian. All rights reserved.
7. //
9. #import <Foundation/Foundation.h>
10. #import "Dog.h"
11. #import "Person.h"
13. int main(int argc, const char * argv[])
14. {
16.     @autoreleasepool {
17.         
18.         Dog * dog1 = [[Dog alloc] init];
19.         
20.         Dog * dog2 = [[Dog alloc] init];
21.         
22.         Person * sim = [[Person alloc] init];
23.         
24.         Person * sian = [[Person alloc] init];
25.         
26.         [dog1 setID:1];
27.         
28.         [dog2 setID:2];
29.         
30.         NSLog(@"//初始化两条狗");
31.         NSLog(@"dog %d retainCount1 is %ld",[dog1 ID],[dog1 retainCount]);
32.         NSLog(@"dog %d retainCount1 is %ld",[dog2 ID],[dog2 retainCount]);
33.         
34.         [sim setDog:dog1];//sim开始遛狗dog1
35.         
36.         NSLog(@"//sim开始遛狗dog1");
37.         NSLog(@"dog %d retainCount2 is %ld",[dog1 ID],[dog1 retainCount]);
38.         NSLog(@"dog %d retainCount2 is %ld",[dog2 ID],[dog2 retainCount]);
39.         
40.         [sian setDog:dog1];//sian开始遛狗dog1
41.         
42.         NSLog(@"//sian开始遛狗dog1");
43.         NSLog(@"dog %d retainCount3 is %ld",[dog1 ID],[dog1 retainCount]);
44.         NSLog(@"dog %d retainCount3 is %ld",[dog2 ID],[dog2 retainCount]);
45.         
46.         [sim setDog:dog2];//sim开始遛狗dog2
47.         
48.         NSLog(@"//sim开始遛狗dog2");
49.         NSLog(@"dog %d retainCount4 is %ld",[dog1 ID],[dog1 retainCount]);
50.         NSLog(@"dog %d retainCount4 is %ld",[dog2 ID],[dog2 retainCount]);
51.         
52.         [sian setDog:dog2];//sian开始遛狗dog2
53.         
54.         NSLog(@"//sian开始遛狗dog2");
55.         NSLog(@"dog %d retainCount5 is %ld",[dog1 ID],[dog1 retainCount]);
56.         NSLog(@"dog %d retainCount5 is %ld",[dog2 ID],[dog2 retainCount]);
57.         
58.         [sim release];//sim离开
59.         
60.         NSLog(@"//sim离开");
61.         NSLog(@"dog %d retainCount6 is %ld",[dog1 ID],[dog1 retainCount]);
62.         NSLog(@"dog %d retainCount6 is %ld",[dog2 ID],[dog2 retainCount]);
63.         
64.         [sian release];//sian离开
65.         
66.         NSLog(@"//sian离开");
67.         NSLog(@"dog %d retainCount7 is %ld",[dog1 ID],[dog1 retainCount]);
68.         NSLog(@"dog %d retainCount7 is %ld",[dog2 ID],[dog2 retainCount]);
69.         
70.         NSLog(@"//dog1 and dog2 is release");
71.         [dog1 release];
72.         [dog2 release];
73.         
74.         
75.     }
76.     return 0;
77. }

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输出结果：

1. 2014-01-11 23:08:52.260 memory[834:303] //初始化两条狗
2. 2014-01-11 23:08:52.261 memory[834:303] dog 1 retainCount1 is 1
3. 2014-01-11 23:08:52.261 memory[834:303] dog 2 retainCount1 is 1
4. 2014-01-11 23:08:52.262 memory[834:303] //sim开始遛狗dog1
5. 2014-01-11 23:08:52.262 memory[834:303] dog 1 retainCount2 is 2
6. 2014-01-11 23:08:52.262 memory[834:303] dog 2 retainCount2 is 1
7. 2014-01-11 23:08:52.263 memory[834:303] //sian开始遛狗dog1
8. 2014-01-11 23:08:52.263 memory[834:303] dog 1 retainCount3 is 3
9. 2014-01-11 23:08:52.263 memory[834:303] dog 2 retainCount3 is 1
10. 2014-01-11 23:08:52.264 memory[834:303] //sim开始遛狗dog2
11. 2014-01-11 23:08:52.264 memory[834:303] dog 1 retainCount4 is 2
12. 2014-01-11 23:08:52.264 memory[834:303] dog 2 retainCount4 is 2
13. 2014-01-11 23:08:52.265 memory[834:303] //sian开始遛狗dog2
14. 2014-01-11 23:08:52.265 memory[834:303] dog 1 retainCount5 is 1
15. 2014-01-11 23:08:52.265 memory[834:303] dog 2 retainCount5 is 3
16. 2014-01-11 23:08:52.266 memory[834:303] Person is dealloc!
17. 2014-01-11 23:08:52.266 memory[834:303] //sim离开
18. 2014-01-11 23:08:52.266 memory[834:303] dog 1 retainCount6 is 1
19. 2014-01-11 23:08:52.267 memory[834:303] dog 2 retainCount6 is 2
20. 2014-01-11 23:08:52.267 memory[834:303] Person is dealloc!
21. 2014-01-11 23:08:52.267 memory[834:303] //sian离开
22. 2014-01-11 23:08:52.268 memory[834:303] dog 1 retainCount7 is 1
23. 2014-01-11 23:08:52.268 memory[834:303] dog 2 retainCount7 is 1
24. 2014-01-11 23:08:52.268 memory[834:303] //dog1 and dog2 is release
25. 2014-01-11 23:08:52.269 memory[834:303] Dog 1 is dealloc!
26. 2014-01-11 23:08:52.269 memory[834:303] Dog 2 is dealloc!
27. Program ended with exit code: 0

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