Objective-C语法之动态门类(isKindOfClass, isMemberOfClass,id)等

Objective-C语法之动态类型(isKindOfClass, isMemberOfClass,id)等

对象在运行时获取其类型的能力称为内省。内省可以有多种方法实现。

判断对象类型

-(BOOL) isKindOfClass: classObj判断是否是这个类或者这个类的子类的实例

-(BOOL) isMemberOfClass: classObj 判断是否是这个类的实例

ps：本篇新建的类主要用于熟悉本篇内容设计，未考虑内存管理因素。

我们试试这两个方法的使用。

1、新建Person类继承NSObject,新建Teacher类继承Person

1.1、新建Person类

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

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1. #import?"Person.h"??
2. ??
3. @implementation?Person??
4. -(void)setName:(NSString?*)n??
5. {??
6. ????name?=?n;??
7. }??
8. ??
9. @end??

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1.2新建Teacher类

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1. #import?"Person.h"??
2. ??
3. @interface?Teacher?:?Person??
4. ??
5. -(void)teach;??
6. ??
7. @end??

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1. #import?"Teacher.h"??
2. ??
3. @implementation?Teacher??
4. -(void)teach??
5. {??
6. ????NSLog(@"我教数学");??
7. }??
8. @end??

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1.3 我们先实验下isMemberOfClass方法。

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1. NSAutoreleasePool?*pool?=?[[NSAutoreleasePool?alloc]?init];??
2. ???Person?*person?=?[[Person?alloc]?init];??
3. ???Teacher?*teacher?=?[[Teacher?alloc]?init];??
4. ?????
5. ???//YES??
6. ???if?([teacher?isMemberOfClass:[Teacher?class]])?{??
7. ????????NSLog(@"teacher?Teacher类的成员");??
8. ???}??
9. ???//NO??
10. ???if?([teacher?isMemberOfClass:[Person?class]])?{??
11. ???????NSLog(@"teacher?Person类的成员");??
12. ???}??
13. ???//NO??
14. ???if?([teacher?isMemberOfClass:[NSObject?class]])?{??
15. ???????NSLog(@"teacher?NSObject类的成员");??
16. ???}??
17. ???[person?release];??
18. ???[teacher?release];??
19. ???[pool?release];??

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打印结果：

2012-07-04 14:23:07.965 ObjectiveCTest[2460:f803] teacher Teacher只有第一个判断打印出来，isMemberOfClass判断是否是属于这类的实例，是否跟父类有关系他不管。

1.4?isKindOfClass方法

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1. NSAutoreleasePool?*pool?=?[[NSAutoreleasePool?alloc]?init];??
2. Person?*person?=?[[Person?alloc]?init];??
3. Teacher?*teacher?=?[[Teacher?alloc]?init];??
4. ??
5. //YES??
6. if?([teacher?isKindOfClass:[Teacher?class]])?{??
7. ????NSLog(@"teacher?是?Teacher类或Teacher的子类");??
8. }??
9. //YES??
10. if?([teacher?isKindOfClass:[Person?class]])?{??
11. ????NSLog(@"teacher?是?Person类或Person的子类");??
12. }??
13. //YES??
14. if?([teacher?isKindOfClass:[NSObject?class]])?{??
15. ????NSLog(@"teacher?是?NSObject类或NSObject的子类");??
16. }??
17. [person?release];??
18. [teacher?release];??
19. [pool?release];??

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2012-07-04 14:34:17.315 ObjectiveCTest[2595:f803] teacher?2012-07-04 14:34:17.316 ObjectiveCTest[2595:f803] teacher?2012-07-04 14:34:17.316 ObjectiveCTest[2595:f803] teacher?[cpp]?view plaincopy

1. //?YES??
2. if?(?[teacher?respondsToSelector:?@selector(?setName:?)]?==?YES?)?{??
3. ????NSLog(@"teacher?responds?to?setSize:?method"?);??
4. }??
5. ??
6. //?NO??
7. if?(?[teacher?respondsToSelector:?@selector(?abcde?)]?==?YES?)?{??
8. ????NSLog(@"teacher?responds?to?nonExistant?method"?);??
9. }??
10. ??
11. //?YES??
12. if?(?[teacher?respondsToSelector:?@selector(?alloc?)]?==?YES?)?{??
13. ????NSLog(@"teacher?class?responds?to?alloc?method\n"?);??
14. }??

打印结果：

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2012-07-04 14:39:49.853 ObjectiveCTest[2723:f803] teacher responds to setSize: method

2012-07-04 14:39:49.854 ObjectiveCTest[2723:f803] teacher class responds to alloc method

中间的那个判断我随便写了个selector,当然没有了。respondsToSelector 检查类方法 alloc返回YES

2.2?instancesRespondToSelector

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1. //?NO??
2. ????if?(?[Person?instancesRespondToSelector:?@selector(teach)]?==?YES?)?{??
3. ????????NSLog(@"Person?instance?responds?to?teach?method"?);??
4. ????}??
5. ??????
6. ????//?YES??
7. ????if?(?[Teacher?instancesRespondToSelector:?@selector(teach)]?==?YES?)?{??
8. ????????NSLog(@"Teacher?instance?responds?to?teach?method");??
9. ????}??
10. ????//?YES??
11. ????if?(?[Teacher?instancesRespondToSelector:?@selector(setName:)]?==?YES?)?{??
12. ????????NSLog(@"Teacher?instance?responds?to?setName:?method"?);??
13. ????}??

打印结果：

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1. 2012-07-04?14:52:29.378?ObjectiveCTest[2961:f803]?Teacher?instance?responds?to?teach?method??
2. 2012-07-04?14:52:29.379?ObjectiveCTest[2961:f803]?Teacher?instance?responds?to?setName:?method??

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3、Objective-C的id类型

C++ 使用的是强类型：对象必须符合其类型，否则不能通过编译。在 Objective-C 中，id类型类似于(void*) ,可以指向任何类的实例。而不需要强制转换。

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下面看看使用，

先把Teacher类中的 teach方法修改一下，改成

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-({

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然后实现并调用

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1. NSAutoreleasePool?*pool?=?[[NSAutoreleasePool?alloc]?init];??
2. Person?*person?=?[[Person?alloc]?init];??
3. Teacher?*teacher?=?[[Teacher?alloc]?init];??
4. ??
5. id?p?=?person;??
6. id?t?=?teacher;??
7. [t?setName:@"张三老师"];??
8. [t?teach];??
9. ??
10. [person?release];??
11. [teacher?release];??
12. [pool?release];??

打印结果：

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1. 2012-07-04?14:57:55.905?ObjectiveCTest[3085:f803]?张三老师?教数学??

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著作权声明：本文由http://blog.csdn.net/totogo2010/原创