理论上category不能声明私有变量，但通过另一种手法，间接实现这样的功能。

.h

import <UIKit/UIKit.h>

@interface UIView (Test)

@property (nonatomic,copy) NSString *name;

@end

.m

import "UIView+Test.h"

import <objc/runtime.h>

@implementation UIView (Test)

• (NSString *)name {

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

}

• (void)setName:(NSString *)value {
  objc_setAssociatedObject(self, @selector(name),value, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
  }

@end