分类(category)的设计分类(category)的设计

1).类中经常容易填满各种方法，而这些方法的代码则会全部堆在一个巨大的实现文件里。在这种情况下，可以用过OC的分类机制，把类代码按逻辑划入几个分区中

#import @interface EOCPerson : NSObject@property(nonatomic, copy, readonly) NSString *firstName; - (id)initWithFirstName:(NSString *)firstName; @end@interface EOCPerson (Friendship) - (void)addFriend:(EOCPerson *)person; @end@interface EOCPerson (Work) - (void)performDayWork; @end

#import "EOCPerson.h" @interface EOCPerson (Friendship) - (void)addFriend:(EOCPerson *)person; @end#import "EOCPerson+Friendship.h" @implementation EOCPerson (Friendship) -(void)addFriend:(EOCPerson *)person { } @end

#import "EOCPerson.h"@interface EOCPerson (Work) -(void)performDayWork; @end#import "EOCPerson+Work.h" @implementation EOCPerson (Work) -(void)performDayWork { } @end

【分类(category)的设计】2).如果有一些私有的方法不想公开，可建一个Private的分类，只在实现文件实现不声明，那就可以做到保密性。
3).为分类添加属性。尽管声明了属性，但分类不会为属性设置set/get方法，类似于@dynamic

@interface EOCPerson (Friendship) @property(nonatomic, strong) NSArray *friends; - (void)addFriend:(EOCPerson *)person; @end#import "EOCPerson+Friendship.h" #import static const char *kFriendsPropertyKey = "kFriendsPropertyKey"; @implementation EOCPerson (Friendship) -(void)addFriend:(EOCPerson *)person {}-(NSArray *)friends { return objc_getAssociatedObject(self, kFriendsPropertyKey); }-(void)setFriends:(NSArray *)friends { objc_setAssociatedObject(self, kFriendsPropertyKey, friends, OBJC_ASSOCIATION_RETAIN_NONATOMIC); }@end