object-c的动态识别与isKindOfClass,isMemberOfClass等

我不是女神ヾ 2023-10-18 21:35 6阅读 0赞

object-c提供了一批用于检测一个对象是不是某个类的对象或成员，它们是isKindOfClass，isMemberOfClass，respondsToSelector，instancesRespondToSelector，performSelector等，  
下面给出了这些函数的一些用法。  
  
  
1.代码：  
// MyRectangle类和Square类略（它们的定义见前一节“8.object-c的继承”），  
// main.m  
\#import "Square.h"  
\#import "MyRectangle.h"  
\#import <stdio.h>  
  
  
int main( int argc, const char \*argv\[\] ) \{  
MyRectangle \*rec = \[\[ MyRectangle alloc\] initWithWidth: 10 height: 20\];  
Square \*sq = \[\[Square alloc\] initWithSize: 15\];  
  
  
// isMemberOfClass  
  
  
// true  
if ( \[sq isMemberOfClass: \[Square class\]\] == YES ) \{  
printf( "square is a member of square class\\n" );  
\}  
  
  
// false  
if ( \[sq isMemberOfClass: \[ MyRectangle class\]\] == YES ) \{  
printf( "square is a member of MyRectangle class\\n" );  
\}  
  
  
// false  
if ( \[sq isMemberOfClass: \[NSObject class\]\] == YES ) \{  
printf( "square is a member of object class\\n" );  
\}  
  
  
// isKindOfClass  
  
// true  
if ( \[sq isKindOfClass: \[Square class\]\] == YES ) \{  
printf( "square is a kind of square class\\n" );  
\}  
  
  
// true  
if ( \[sq isKindOfClass: \[ MyRectangle class\]\] == YES ) \{  
printf( "square is a kind of MyRectangle class\\n" );  
\}  
  
  
// true  
if ( \[sq isKindOfClass: \[NSObject class\]\] == YES ) \{  
printf( "square is a kind of object class\\n" );  
\}  
  
  
// respondsToSelector  
  
  
// true  
if ( \[sq respondsToSelector: @selector( setSize: )\] == YES ) \{  
printf( "square responds to setSize: method\\n" );  
\}  
  
  
// false  
if ( \[sq respondsToSelector: @selector( nonExistant )\] == YES ) \{  
printf( "square responds to nonExistant method\\n" );  
\}  
  
  
// true  
if ( \[Square respondsToSelector: @selector( alloc )\] == YES ) \{  
printf( "square class responds to alloc method\\n" );  
\}  
  
  
  
  
// instancesRespondToSelector  
  
  
// false  
if ( \[ MyRectangle instancesRespondToSelector: @selector( setSize: )\] == YES ) \{  
printf( " MyRectangle instance responds to setSize: method\\n" );  
\}  
  
  
// true  
if ( \[Square instancesRespondToSelector: @selector( setSize: )\] == YES ) \{  
printf( "square instance responds to setSize: method\\n" );  
\}  
  
  
// free memory  
\[rec release\];  
\[sq release\];  
  
return 0;  
\}  
  
  
  
  
2. 运行结果：  
$ ./main.exe  
square is a member of square class  
square is a kind of square class  
square is a kind of MyRectangle class  
square is a kind of object class  
square responds to setSize: method  
square class responds to alloc method  
square instance responds to setSize: method  
  
  
3.说明：  
 （1） 请和jave的instanceof相比较；  
 （2） 请和java的 getClass相比较;  
 （3） 所有继承人自 NSObject 都有一个 class method。