一般認為Category不能新增變數，其實系統已經告訴我們是可以的.

這傢伙已經給UIViewController添加了圖中的幾個屬性,那麼如何實現?

其實是使用@dynamic來動態新增的。 (即執行時Runtime)

程式碼:

1.建立Person類

#import <Foundation/Foundation.h>

@interface Person :NSObject

@property (nonatomic,copy)NSString * name;

@end

2.建立Person的類別

#import "Person.h"

// 新增額外兩個屬性

@interface

@property (nonatomic,assign)NSInteger age;

@property (nonatomic,copy)NSString * stu;

@end

3.Person類別.m的實現

#import "Person+addProperty.h"

#import <objc/runtime.h>

@implementation Person (addProperty)

staticchar nameKey = 'n';

staticchar stuKey = 's';

// 給age屬性提供getter和

- (NSInteger)age{

return [objc_getAssociatedObject(self, &nameKey)integerValue];

}

- (void)setAge:(NSInteger)age {

   NSString * s = [NSStringstringWithFormat:@"%ld",(long)age];

objc_setAssociatedObject(self, &nameKey,s,OBJC_ASSOCIATION_COPY_NONATOMIC);

}

// 給stu屬性提供getter和setter方法

- (NSString*)stu{

returnobjc_getAssociatedObject(self, &stuKey);

}

- (void)setStu:(NSString *)stu{

objc_setAssociatedObject(self, &stuKey, stu,OBJC_ASSOCIATION_COPY_NONATOMIC);

}

@end

4.用一下吧

#import "ViewController.h"

#import "Person+addProperty.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {

    [superviewDidLoad];

   Person * p = [[Personalloc] init];

    p.name =@"原有屬性";

    p.stu =@"新增的屬性";

    p.age =17;

   NSLog(@"%@ %@ %ld",p.name,p.stu,p.age);

}