在第8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：
代码1：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...");
}
@end
int 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");
}