[置頂] Objective-C,/,ios,/iphone開發基礎：分類（category,又稱類别）

在c++中我們可以多繼承來實作代碼複用和封裝使程式更加簡練。在objective-c中隻能單繼承，不能多繼承，那麼除了協定protocol之外，我們可以實作類似多繼承的一個方法就是，分類（category,又稱類别）。類别可以不修改原來的類（父類），和派生類的情況下，為原有的類增加新的方法，但是分類不能增加執行個體變量。

格式（format）：

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

method _declaration;

....

@end

@implementation class_name(category_name)

method_implementation;

...

@end

建立一個AddressCard類，然後再建立一個檔案 AddressCardCategory 用來聲明和實作分類（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 }      

執行結果：

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]

轉載于:https://www.cnblogs.com/james1207/p/3270922.html