1、在.h文件里：

#import 
     
      @interface NSObject (Property)@property (nonatomic, strong) id propretyName;@end
     

2、在.m文件里

#import "NSObject+Property.h"#import 
     
      @implementation NSObject (Property)- (id)propretyName{    return objc_getAssociatedObject(self, @selector(propretyName));}- (void)setPropretyName:(id)propretyName{    objc_setAssociatedObject(self, @selector(propretyName), propretyName, OBJC_ASSOCIATION_RETAIN_NONATOMIC);}@end