[置顶] Objective-C,/,ios,/iphone开发基础：分类（category,又称类别）

 

在c++中我们可以多继承来实现代码复用和封装使程序更加简练。在objective-c中只能单继承，不能多继承，那么除了协议protocol之外，我们可以实现类似多继承的一个方法就是，分类（category,又称类别）。类别可以不修改原来的类（父类），和派生类的情况下，为原有的类增加新的方法，但是分类不能增加实例变量。

格式（format）：

@interface class_name(category_name)<protocol,....>

method _declaration;

....

@end

@implementation class_name(category_name)

method_implementation;

...

@end

新建一个AddressCard类，然后再新建一个文件 AddressCardCategory 用来声明和实现分类（category）

 1 #import <Foundation/Foundation.h>

 2 

 3 @interface AddressCard : NSObject<NSCoding>{

 4     NSString* name;

 5     NSString* email;

 6 }

 7 @property (nonatomic,retain)NSString* name;

 8 @property (nonatomic,retain)NSString* email;

 9 -(id)initWithName:(NSString*)_name andEmail:(NSString*)_email;

10 

11 @end

 

 1 #import "AddressCard.h"

 2 

 3 @implementation AddressCard

 4 @synthesize name,email;

 5 -(id)initWithName:(NSString*)_name andEmail:(NSString*)_email{

 6     if(self= [super init])

 7     {

 8         self.name=_name;

 9         self.email=_email;

10     }

11     return self;

12 }

13 -(void)encodeWithCoder:(NSCoder *)aCoder{

14     [aCoder encodeObject:name forKey:@"_name"];

15     [aCoder encodeObject:email forKey:@"_email"];

16 }

17 

18 -(id)initWithCoder:(NSCoder*)aDecoder{

19     if(self=[super init])

20     {

21         self.name=[aDecoder decodeObjectForKey:@"_name"];

22         self.email=[aDecoder decodeObjectForKey:@"_email"];

23     }

24     return self;

25 }

26 -(void)dealloc{

27     [name release];

28     [email release];

29     [super dealloc];

30 }

31 @end

 

#import <Foundation/Foundation.h>

#import "AddressCard.h"

@interface AddressCard(category)

-(void)uppercaseName;



@end

 

1 #import "AddressCardCategory.h"

2 

3 @implementation AddressCard(Category)

4 -(void)uppercaseName{

5     self.name= [name uppercaseString];

6 }

7 

8 @end

 1 #import <Foundation/Foundation.h>

 2 #import "AddressCardCategory.h"

 3 int main (int argc, const char * argv[])

 4 {

 5 

 6     @autoreleasepool {

 7         AddressCard* card1=[[AddressCard alloc]initWithName:@"shou" andEmail:@"[email protected]"];

 8         [NSKeyedArchiver archiveRootObject:card1 toFile:@"/tmp/AddressCard.txt"];

 9         AddressCard* card4=[NSKeyedUnarchiver unarchiveObjectWithFile:@"/tmp/AddressCard.txt"];

10         NSLog(@"card 4 %@ ,%@",card4.name,card4.email);

11         [card4 uppercaseName];

12          NSLog(@"card 4 %@ ,%@",card4.name,card4.email);

13         [card1 release];

14         //[card4 release];

15         

16         

17     }

18     return 0;

19 }

执行结果：

2013-08-20 17:12:04.751 AddressCard[1079:707] card 4 shou ,[email protected]
2013-08-20 17:12:04.758 AddressCard[1079:707] card 4 SHOU ,[email protected]