category使用 objc_setAssociatedObj

@interface NSObject (CategoryWithProperty)

@property (nonatomic, strong) NSObject *property;

@end

@implementation NSObject (CategoryWithProperty)

- (NSObject *)property {

return objc_getAssociatedObject(self, @selector(property));

}

- (void)setProperty:(NSObject *)value {

objc_setAssociatedObject(self, @selector(property), value, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

}

@end