篇文章里我们来聊聊如何扩展一个类的方法和实例变量，我们首先来看一下命名分类如何扩展一个类。在下面的代码中，首先定义一个类Player用来定义普通球员，如果第三方开发者发现普通球员缺少了一些方法，则可以用分类ext来扩充喽：
：默认的Player类
Player.h文件:
#import<Foundation/Foundation.h>@interfacePlayer:NSObject{intnumber;intage;}-(void)show;-(id)init:(int)n:(int)age;@end
Player.m文件：
#import"Player.h"@implementationPlayer-(id)init:(int)n:(int)age_v{self= [super init];if(self){number= n;age= age_v;}returnself;}-(void)show{NSLog(@"playerx ,number:%d,age:%d",number,age);}@end
test.m文件：
#import"Player.h"intmain(int argc,char **argv){@autoreleasepool{Player*p = [[Player alloc] init: 1 :20];[pshow];}return0;}
编译执行结果如下：
apple@kissAir:Player$clang -fobjc-arc -framework Foundation
Player.m test.m -o main
apple@kissAir:Player$./main
2014-06-3017:55:56.053 main[3862:507] player
x ,number:1,age:20
现在一个第三方软件公司觉得球员球员太不活泼，so他们决定给球员添加方法say和train:
Player_ext.h文件
#import"Player.h"@interfacePlayer (ext)//@propertyint power;//-(id)init:(int)n:(int)age :(int)power;-(void)say;-(void)train;@end
Player_ext.m文件
#import"Player_ext.h"@implementationPlayer (ext)//@synthesizepower;/*-(id)init:(int)n :(int)age_v :(int)pow{self= [super init :n :age_v];if(self){power= pow;}returnself;}*/-(void)say{NSLog(@"player[n:%d]want to say : hello!",number);}-(void)train{NSLog(@"player[n:%d]is training...",number);}@end
test.m文件
//#import"Player.h"#import"Player_ext.h"intmain(int argc,char **argv){@autoreleasepool{Player*p = [[Player alloc] init: 1 :20];[pshow];[psay];[ptrain];}return0;}
我们编译运行看看结果咯：
apple@kissAir:Player$clang -fobjc-arc -framework Foundation
Player.m Player_ext.mtest.m -o main
apple@kissAir:Player$./main
2014-06-3018:16:09.050 main[4246:507] player
x ,number:1,age:20
2014-06-3018:16:09.052 main[4246:507] player[n:1]
want to say : hello!
2014-06-3018:16:09.053 main[4246:507] player[n:1]
is training…
我们发现在命名分类中试图添加实例变量是不允许的，只能在未命名分类中添加，而且未命名分类中声明方法的实现只能放在主类的实现中。下面修改代码，增加power属性，并且train动作是要耗费power的，遂修改该方法，同时新增init方法如下：
@implementation Player (ext)//@synthesize power;/*-(id)init :(int)n :(int)age_v :(int)pow{self = [super init :n :age_v];if(self){power = pow;}return self;}*/-(void)say{NSLog(@"player[n:%d] want to say : hello!",number);}-(void)train{NSLog(@"player[n:%d:pow:%d] is training...power is down to %d",\number,self.power,self.power -= 10);}
Player.h文件
#import <Foundation/Foundation.h>@interface Player:NSObject{int number;int age;}-(void)show;-(id)init:(int)n :(int)age;@end@interface Player ()@property int power;-(id)init :(int)n :(int)age :(int)power;@end
Player.m文件
#import "Player.h"@implementation Player@synthesize power;-(id)init:(int)n :(int)age_v{self = [super init];if(self){number = n;age = age_v;}return self;}-(id)init :(int)n :(int)age_v :(int)pow{self = [super init];if(self){self = [self init :n :age_v];power = pow;}return self;}-(void)show{NSLog(@"player x ,number:%d,age:%d,power:%d",number,age,power);}@end
test.m文件
#import "Player_ext.h"int main(int argc,char **argv){@autoreleasepool{Player *p = [[Player alloc] init: 1 :20 :100];[p show];[p say];[p train];[p show];}return 0;}
编译运行结果如下：
apple@kissAir: Player$clang -fobjc-arc -framework Foundation Player.m Player_ext.m test.m -o main
apple@kissAir: Player$./main
2014-06-30 18:52:29.237 main[4822:507] player x ,number:1,age:20,power:100
2014-06-30 18:52:29.239 main[4822:507] player[n:1] want to say : hello!
2014-06-30 18:52:29.240 main[4822:507] player[n:1:pow:100] is training…power is down to 90
2014-06-30 18:52:29.240 main[4822:507] player x ,number:1,age:20,power:90
有球员就有教练啊，现在添加教练类。教练类和球员类有共性的地方哦，就是都有say和train方法。这个共性的地方不妨就用协议来描述吧，需要说明的是教练还有一个召开发布会方法，该方法球员是没有的，我们把它作为一个可选方法放入协议。为了方便就把教练类放在test.m中喽：
Player.h文件
#import <Foundation/Foundation.h>@protocol Actions-(void)say;//必须存在@optional-(void)convoke; //可选方法@required-(void)train; //必须存在@end@interface Player:NSObject{int number;int age;}-(void)show;-(id)init:(int)n :(int)age;@end@interface Player ()@property int power;-(id)init :(int)n :(int)age :(int)power;@end
Player_ext.h文件
#import "Player.h"@interface Player (ext) <Actions>//@property int power;//-(id)init:(int)n :(int)age :(int)power;-(void)say;-(void)train;@end
test.m文件
//#import "Player.h"#import "Player_ext.h"@interface Coach:NSObject <Actions>@end@implementation Coach-(void)say{NSLog(@"coach say : hello!");}-(void)train{NSLog(@"coach is leading train...");}-(void)convoke{NSLog(@"coach is convoking a meeting...");}@endint main(int argc,char **argv){@autoreleasepool{Player *p = [[Player alloc] init: 1 :20 :100];Coach *c = [[Coach alloc] init];[p show];[c say];[c convoke];[c train];[p say];[p train];[p show];}return 0;}
编译运行结果如下：
apple@kissAir: Player$./main
2014-06-30 20:33:24.930 main[6466:507] player x ,number:1,age:20,power:100
2014-06-30 20:33:24.932 main[6466:507] coach say : hello!
2014-06-30 20:33:24.933 main[6466:507] coach is convoking a meeting…
2014-06-30 20:33:24.933 main[6466:507] coach is leading train…
2014-06-30 20:33:24.934 main[6466:507] player[n:1] want to say : hello!
2014-06-30 20:33:24.934 main[6466:507] player[n:1:pow:100] is training…power is down to 90
2014-06-30 20:33:24.934 main[6466:507] player x ,number:1,age:20,power:90
如果要添加多个协议语法为: @interface A <p_a,p_b>
最后我们可以用反射方法测试类是否遵守协议：
Protocol *actions = @protocol(Actions);Player *p = [[Player alloc] init: 1 :20 :100];Coach *c = [[Coach alloc] init];if([p conformsToProtocol: actions]){NSLog(@"Player abide protocol Actions"); //Coach同样遵守}//对于可选方法我们可以用一般的respondsToSelector方法来测试:if([c respondsToSelector :@selector(convoke)]){NSLog(@"Coach has convoke method");}
