ObjC(Objective-C)中的Class(类类型),Selector(选择器SEL),函数指针(IMP)

1

#import <Foundation/Foundation.h>

2

3

@interface

Cattle :

NSObject

{

4

int

legsCount;

5

}

6

- (

void

)saySomething;

7

- (

void

)setLegsCount:(

int

) count;

8

@end

01

#import "Cattle.h"

02

03

@implementation

Cattle

04

05

-(

void

) saySomething

06

{

07

NSLog

(@

"Hello,I am a cattle,I have %d legs."

,legsCount);

08

}

09

10

-(

void

) setLegsCount:(

int

) count

11

{

12

legsCount = count;

13

}

14

@end

01

#import <Foundation/Foundation.h>

02

#import "Cattle.h"

03

04

@interface

Bull : Cattle {

05

NSString

*skinColor;

06

}

07

- (

void

)saySomething;

08

- (

NSString

*) getSkinColor;

09

- (

void

) setSkinColor:(

NSString

*) color;

10

@end

01

#import "Bull.h"

02

03

04

@implementation

Bull

05

06

-(

void

) saySomething

07

{

08

NSLog

(@

"Hello,I am a %@ bull,I have %d legs."

,[

self

getSkinColor],legsCount);

09

}

10

11

-(

NSString

*) getSkinColor

12

{

13

return

skinColor;

14

}

15

16

- (

void

) setSkinColor:(

NSString

*) color

17

{

18

skinColor = color;

19

}

20

@end

01

#import <Foundation/Foundation.h>

02

03

//定义几个字符串常量

04

#define SET_SKIN_COLOR @"setSkinColor:"

05

#define BULL_CLASS @"Bull"

06

#define CATTLE_CLASS @"Cattle"

07

08

09

@interface

DoProxy :

NSObject

{

10

BOOL

notFirstRun;

11

12

id

cattle[3];

13

//定义二个选择器

14

SEL

say;

15

SEL

skin;

16

17

//定义一个函数指针(传统C语言的处理方式)

18

void

(*setSkinColor_Func)(

id

,

SEL

,

NSString

*);

19

20

//定义一个IMP方式的函数指针(obj-C中推荐的方式)

21

IMP say_Func;

22

23

//定义一个类

24

Class bullClass;

25

}

26

27

-(

void

) doWithCattleId:(

id

) aCattle colorParam:(

NSString

*) color;

28

-(

void

) setAllIVars;

29

-(

void

) SELFuncs;

30

-(

void

) functionPointers;

31

32

@end

01

#import "DoProxy.h"

02

#import "Cattle.h"

03

#import "Bull.h"

04

05

@implementation

DoProxy

06

07

08

//初始化所有变量

09

- (

void

) setAllIVars

10

{

11

cattle[0] = [Cattle

new

];

12

13

bullClass =

NSClassFromString

(BULL_CLASS);

14

//即cattle[1],cattle[2]都是Bull类的实例

15

cattle[1] = [bullClass

new

];

16

cattle[2] = [bullClass

new

];

17

18

say =

@selector

(saySomething);

19

skin =

NSSelectorFromString

(SET_SKIN_COLOR);

20

}

21

22

23

//初始化id

24

- (

void

) doWithCattleId:(

id

) aCattle colorParam:(

NSString

*) color

25

{

26

//第一次运行的时候

27

if

(notFirstRun ==

NO

)

28

{

29

NSString

*myName =

NSStringFromSelector

(_cmd);

//取得当前正在执行的方法的名字

30

NSLog

(@

"Running in the method of %@"

,myName);

31

notFirstRun =

YES

;

//修改初次运行标志位

32

}

33

34

NSString

*cattleParamClassName = [aCattle className];

//取得aCattle的"类名称"

35

36

//如果aCattle是Bull或Cattle类的实例

37

if

([cattleParamClassName isEqualToString:BULL_CLASS] || [cattleParamClassName isEqualToString:CATTLE_CLASS])

38

{

39

[aCattle setLegsCount:4];

//设置牛的4条腿

40

if

([aCattle respondsToSelector:skin])

//如果aCattle对应的是类中,有定义方法"setSkinColor"

41

{

42

[aCattle performSelector:skin withObject:color];

//则调用setSkinColor方法

43

}

44

else

45

{

46

NSLog

(@

"Hi,I am a %@,have not setSkinColor!"

,cattleParamClassName);

//否则输出相应的提示信息

47

}

48

[aCattle performSelector:say];

//最后执行saySomething方法(这二个方法在Bull与Cattle类中都有,所以肯定能运行)

49

}

50

else

//如果aCattle即不是Bull类也不是Cattle类的实例

51

{

52

NSString

*yourClassName = [aCattle className];

53

NSLog

(@

"Hi,you are a %@,but I like cattle or bull!"

,yourClassName);

//显示这个"异类"的相关信息

54

}

55

}

56

57

//初始化选择器以及相应函数

58

- (

void

) SELFuncs

59

{

60

[

self

doWithCattleId:cattle[0] colorParam:@

"brown"

];

61

[

self

doWithCattleId:cattle[1] colorParam:@

"red"

];

62

[

self

doWithCattleId:cattle[2] colorParam:@

"black"

];

63

[

self

doWithCattleId:

self

colorParam:@

"haha"

];

//这里故意传入一个异类self(即DoProxy本身),DoProxy当然不是Bull或Cattle

64

}

65

66

//函数指针测试

67

- (

void

) functionPointers

68

{

69

//取得函数指针的第一种方式

70

setSkinColor_Func=(

void

(*)(

id

,

SEL

,

NSString

*)) [cattle[1] methodForSelector:skin];

71

//上面的语句其实等效于下面这种方法

72

//IMP setSkinColor_Func = [cattle[1] methodForSelector:skin];

73

74

//用第二种方法取得saySomething的函数指针

75

say_Func = [cattle[1] methodForSelector:say];

76

77

//用函数指针的形式调用setSkinColor

78

setSkinColor_Func(cattle[1],skin,@

"verbose"

);

79

80

NSLog

(@

"Running as a function pointer will be more efficiency!"

);

81

82

//调用saySomething方法

83

say_Func(cattle[1],say);

84

}

85

86

@end

01

#import <Foundation/Foundation.h>

02

#import "DoProxy.h"

03

04

int

main (

int

argc,

const

char

* argv[]) {

05

NSAutoreleasePool

* pool = [[

NSAutoreleasePool

alloc] init];

06

DoProxy *doProxy = [DoProxy

new

];

07

08

[doProxy setAllIVars];

09

[doProxy SELFuncs];

10

[doProxy functionPointers];

11

12

[doProxy release];

13

[pool drain];

14

return

0;

15

}