objective-C中的Class(類類型),Selector(選擇器SEL),函數(shù)指針(IMP)
今天在園子里看到了一篇牛文“Objective-C 2.0 with Cocoa Foundation--- 5见咒，Class類型额嘿，選擇器Selector以及函數(shù)指針 ”畔柔，講得十分精彩赂弓，忍不住把它的代碼加上注釋整理于此忌堂，以便日后查看描验。
個(gè)人體會(huì)：obj-C中的“Class類型變量”比c#中的Object基類還要靈活占哟，可以用它生成任何類型的實(shí)例（但是它又不是NSObject）。而選擇器SEL與函數(shù)指針I(yè)MP翩迈，如果非要跟c#扯上關(guān)系的話持灰，這二個(gè)結(jié)合起來，就點(diǎn)類似c#中的反射+委托负饲，可以根據(jù)一個(gè)方法名稱字符串堤魁，直接調(diào)用方法。
"牛"的基類 Cattle.h
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import <Foundation/Foundation.h>
@interface Cattle : NSObject {
int legsCount;
}
- (void)saySomething;
- (void)setLegsCount:(int) count;
@end
Cattle.m
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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
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import <Foundation/Foundation.h>
import "Cattle.h"
@interface Bull : Cattle {
NSString *skinColor;
}
- (void)saySomething;
- (NSString*) getSkinColor;
- (void) setSkinColor:(NSString *) color;
@end
Bull.m
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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)
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import <Foundation/Foundation.h>
//定義幾個(gè)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(gè)選擇器
SEL say;
SEL skin;
//定義一個(gè)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(gè)IMP方式的函數(shù)指針(obj-C中推薦的方式)
IMP say_Func;
//定義一個(gè)類
Class bullClass;
}
-(void) doWithCattleId:(id) aCattle colorParam:(NSString*) color;
-(void) setAllIVars;
-(void) SELFuncs;
-(void) functionPointers;
@end
DoProxy.m
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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(shí)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(yùn)行的時(shí)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(yùn)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(shí)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(gè)方法在Bull與Cattle類中都有,所以肯定能運(yùn)行)
}
else //如果aCattle即不是Bull類也不是Cattle類的實(shí)例
{
NSString *yourClassName = [aCattle className];
NSLog(@"Hi, you are a %@, but I like cattle or bull!", yourClassName);//顯示這個(gè)"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(gè)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(shí)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()
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import <Foundation/Foundation.h>
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(yùn)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.
作者：菩提樹下的楊過
出處：http://yjmyzz.cnblogs.com
本文版權(quán)歸作者和博客園共有返十，歡迎轉(zhuǎn)載妥泉，但未經(jīng)作者同意必須保留此段聲明，且在文章頁面明顯位置給出原文連接洞坑，否則保留追究法律責(zé)任的權(quán)利盲链。
