個人體會：obj-C中的“Class類型變量”比c#中的Object基類還要靈活梦重，可以用它生成任何類型的實例（但是它 又不是NSObject）。而選擇器SEL與函數(shù)指針I(yè)MP鱼炒，如果非要跟c#扯上關(guān)系的話，這二個結(jié)合起來蝌借，就點類似c#中的反射+委托昔瞧，可以根據(jù)一個方 法名稱字符串，直接調(diào)用方法菩佑。
"牛"的基類 Cattle.h
#import
@interface Cattle : NSObject {
int legsCount;
}
- (void)saySomething;
- (void)setLegsCount:(int) count;
@end
Cattle.m
#import "Cattle.h"
@implementation Cattle
-(void) saySomething
{
NSLog(@"Hello, I am a cattle, I have %d legs.", legsCount);
}
-(void) setLegsCount:(int) count
{
legsCount = count;
}
@end
子類“公牛" Bull.h
#import
#import "Cattle.h"
@interface Bull : Cattle {
NSString *skinColor;
}
- (void)saySomething;
- (NSString*) getSkinColor;
- (void) setSkinColor:(NSString *) color;
@end
Bull.m
#import "Bull.h"
@implementation Bull
-(void) saySomething
{
NSLog(@"Hello, I am a %@ bull, I have %d legs.", [self getSkinColor],legsCount);
}
-(NSString*) getSkinColor
{
return skinColor;
}
- (void) setSkinColor:(NSString *) color
{
skinColor = color;
}
@end
代理類DoProxy.h (關(guān)鍵的代碼都在這里)
#import
//定義幾個字符串常量
#define SET_SKIN_COLOR @"setSkinColor:"
#define BULL_CLASS @"Bull"
#define CATTLE_CLASS @"Cattle"
@interface DoProxy : NSObject {
BOOL notFirstRun;
id cattle[3];
//定義二個選擇器
SEL say;
SEL skin;
//定義一個函數(shù)指針(傳統(tǒng)C語言的處理方式)
void(*setSkinColor_Func)(id,SEL,NSString*);
//定義一個IMP方式的函數(shù)指針(obj-C中推薦的方式)
IMP say_Func;
//定義一個類
Class bullClass;
}
-(void) doWithCattleId:(id) aCattle colorParam:(NSString*) color;
-(void) setAllIVars;
-(void) SELFuncs;
-(void) functionPointers;
@end
DoProxy.m
#import "DoProxy.h"
#import "Cattle.h"
#import "Bull.h"
@implementation DoProxy
//初始化所有變量
- (void) setAllIVars
{
cattle[0] = [Cattle new];
bullClass = NSClassFromString(BULL_CLASS);
//即cattle[1],cattle[2]都是Bull類的實例
cattle[1] = [bullClass new];
cattle[2] = [bullClass new];
say = @selector(saySomething);
skin = NSSelectorFromString(SET_SKIN_COLOR);
}
//初始化id
- (void) doWithCattleId:(id) aCattle colorParam:(NSString*) color
{
//第一次運行的時候
if(notFirstRun == NO)
{
NSString *myName = NSStringFromSelector(_cmd);//取得當(dāng)前正在執(zhí)行的方法的名字
NSLog(@"Running in the method of %@", myName);
notFirstRun = YES;//修改初次運行標(biāo)志位
}
NSString *cattleParamClassName = [aCattle className];//取得aCattle的"類名稱"
//如果aCattle是Bull或Cattle類的實例
if([cattleParamClassName isEqualToString:BULL_CLASS] || [cattleParamClassName isEqualToString:CATTLE_CLASS])
{
[aCattle setLegsCount:4];//設(shè)置牛的4條腿
if([aCattle respondsToSelector:skin])//如果aCattle對應(yīng)的是類中,有定義方法"setSkinColor"
{
[aCattle performSelector:skin withObject:color];//則調(diào)用setSkinColor方法
}
else
{
NSLog(@"Hi, I am a %@, have not setSkinColor!", cattleParamClassName);//否則輸出相應(yīng)的提示信息
}
[aCattle performSelector:say];//最后執(zhí)行saySomething方法(這二個方法在Bull與Cattle類中都有,所以肯定能運行)
}
else //如果aCattle即不是Bull類也不是Cattle類的實例
{
NSString *yourClassName = [aCattle className];
NSLog(@"Hi, you are a %@, but I like cattle or bull!", yourClassName);//顯示這個"異類"的相關(guān)信息
}
}
//初始化選擇器以及相應(yīng)函數(shù)
- (void) SELFuncs
{
[self doWithCattleId:cattle[0] colorParam:@"brown"];
[self doWithCattleId:cattle[1] colorParam:@"red"];
[self doWithCattleId:cattle[2] colorParam:@"black"];
[self doWithCattleId:self colorParam:@"haha"];//這里故意傳入一個異類self(即DoProxy本身),DoProxy當(dāng)然不是Bull或Cattle
}
//函數(shù)指針測試
- (void) functionPointers
{
//取得函數(shù)指針的第一種方式
setSkinColor_Func=(void (*)(id, SEL, NSString*)) [cattle[1] methodForSelector:skin];
//上面的語句其實等效于下面這種方法
//IMP setSkinColor_Func = [cattle[1] methodForSelector:skin];
//用第二種方法取得saySomething的函數(shù)指針
say_Func = [cattle[1] methodForSelector:say];
//用函數(shù)指針的形式調(diào)用setSkinColor
setSkinColor_Func(cattle[1],skin,@"verbose");
NSLog(@"Running as a function pointer will be more efficiency!");
//調(diào)用saySomething方法
say_Func(cattle[1],say);
}
@end
測試主函數(shù)main()
#import
#import "DoProxy.h"
int main (int argc, const char * argv[]) {
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
DoProxy *doProxy = [DoProxy new];
[doProxy setAllIVars];
[doProxy SELFuncs];
[doProxy functionPointers];
[doProxy release];
[pool drain];
return 0;
}
運行結(jié)果：
2011-02-28 21:40:33.240 HelloSelector[630:a0f] Running in the method of doWithCattleId:colorParam:
2011-02-28 21:40:33.245 HelloSelector[630:a0f] Hi, I am a Cattle, have not setSkinColor!
2011-02-28 21:40:33.247 HelloSelector[630:a0f] Hello, I am a cattle, I have 4 legs.
2011-02-28 21:40:33.248 HelloSelector[630:a0f] Hello, I am a red bull, I have 4 legs.
2011-02-28 21:40:33.250 HelloSelector[630:a0f] Hello, I am a black bull, I have 4 legs.
2011-02-28 21:40:33.251 HelloSelector[630:a0f] Hi, you are a DoProxy, but I like cattle or bull!
2011-02-28 21:40:33.252 HelloSelector[630:a0f] Running as a function pointer will be more efficiency!
2011-02-28 21:40:33.254 HelloSelector[630:a0f] Hello, I am a verbose bull, I have 4 legs
