objective-c中的构造函数（对象初始化）（七）

holydancer原创，如需转载，请在显要位置注明：

转自holydancer的CSDN专栏，原文地址：http://blog.csdn.net/holydancer/article/details/7354489

?

? ? ? ?以前我们创建对象时都是用new，从java过来的同学也都有这种习惯，其实objective-c中还有一种地道的创建对象的方法：[ [类名 alloc ] init].这种方法才是OC中创建对象的正统，不过效果和new是一样的，但是这种方法更能表示创建对象的实质，那就是分配内存，初始化对象。

alloc是在内存中划分一片空间，这片空间是一片处女地，然后呢，init初始化，我们可以在初始化的时候设置一些基本属性的值，这样就不用在创建对象后再调用方法来赋值。看代码：

human.h:

?

[plain]?view plaincopy?

1. #import?<Foundation/Foundation.h>??
2. ??
3. @interface?Human?:?NSObject??
4. {??
5. ????int?age;??
6. ????NSString?*name;??
7. }??
8. -(void)setAge:(int)a?setName:(NSString?*)n;??
9. -(int)age;??
10. -(NSString?*)name;??
11. @end??

human.m:

?

?

[plain]?view plaincopy?

1. #import?"Human.h"??
2. ??
3. @implementation?Human??
4. -(id)init??
5. {??
6. ????if(self=[super?init])??
7. ????{??
8. ????????age=20;??
9. ????????name=@"holy";??
10. ????}??
11. ????return?self;??
12. }??
13. -(void)setAge:(int)a?setName:(NSString?*)n??
14. {??
15. ????age=a;??
16. ????[name?release];??
17. ??????
18. ????name=[n?copy];??
19. }??
20. -(int)age??
21. {??
22. ????return?age;??
23. }??
24. -(NSString?*)name??
25. {??
26. ????return?name;??
27. }??
28. @end??

main.m:

?

?

[plain]?view plaincopy?

1. #import?<Foundation/Foundation.h>??
2. #import?"Human.h"??
3. int?main(int?argc,?const?char?*?argv[])??
4. {??
5. ????NSAutoreleasePool?*pool;??
6. ????pool?=[[NSAutoreleasePool?alloc]?init];??
7. ??????
8. ????Human?*?human?=?[[Human?alloc]?init];??
9. ????NSLog(@"名字%@,年龄%d",[human?name],[human?age]);??
10. ??????
11. ????[human?setAge:100?setName:@"GOD"];??
12. ????NSLog(@"名字%@,年龄%d",[human?name],[human?age]);??
13. ??
14. ????[human?release];??
15. ????[pool?release];//相当于对池中每个对象执行了一次release;??
16. ??????
17. ??
18. }??

?

?

上面的代码，在其中有一行这种初始化方法很好理解，但是有个缺点就是生成对象的默认属性值是固定的，如果想要修改的话需要再调用[plain]?view plaincopy?

1. #import?<Foundation/Foundation.h>??
2. ??
3. @interface?Human?:?NSObject??
4. {??
5. ????int?age;??
6. ????NSString?*name;??
7. }??
8. -(id)initWithAge:(int)a?Name:(NSString?*)n;??
9. -(int)age;??
10. -(NSString?*)name;??
11. @end??

Human.m:

?

?

[plain]?view plaincopy?

1. #import?"Human.h"??
2. ??
3. @implementation?Human??
4. -(id)init??
5. {??
6. ????if(self=[super?init])??
7. ????{??
8. ????????age=20;??
9. ????????name=@"holy";??
10. ????}??
11. ????return?self;??
12. }??
13. -(id)initWithAge:(int)a?Name:(NSString?*)n??
14. {??
15. ????if?(self=[super?init])?{??
16. ????????age=a;??
17. ????????[name?release];??
18. ??????????
19. ????????name=[n?copy];??
20. ????}??
21. ????return?self;??
22. ?????
23. }??
24. -(int)age??
25. {??
26. ????return?age;??
27. }??
28. -(NSString?*)name??
29. {??
30. ????return?name;??
31. }??
32. @end??

main.m:

?

?

[plain]?view plaincopy?

1. #import?<Foundation/Foundation.h>??
2. #import?"Human.h"??
3. int?main(int?argc,?const?char?*?argv[])??
4. {??
5. ????NSAutoreleasePool?*pool;??
6. ????pool?=[[NSAutoreleasePool?alloc]?init];??
7. ??????
8. ????Human?*?human1?=?[[Human?alloc]?init];??
9. ????NSLog(@"名字%@,年龄%d",[human1?name],[human1?age]);??
10. ??????
11. ????Human?*?human2?=?[[Human?alloc]?initWithAge:100?Name:@"GOD"];??
12. ????NSLog(@"名字%@,年龄%d",[human2?name],[human2?age]);??
13. ??????
14. ??????
15. ????[human1?release];??
16. ????[human2?release];??
17. ????[pool?release];//相当于对池中每个对象执行了一次release;??
18. ??????
19. ??
20. }??

输出：

?

?

[plain]?view plaincopy?

1. 2012-03-14?21:03:24.974?String[460:403]?名字holy,年龄20??
2. 2012-03-14?21:03:24.976?String[460:403]?名字GOD,年龄100??

[plain]?view plaincopy?

1. 关键字：objective-c?，objective?c?，?oc?，构造函数?，对象初始化?

?