这一点上有两点要表达一下：第一，XCode运行你在Category的.h文件申明@Property，编译通过，但运行时如果没有Runtime处理，进行赋值取值，就马上报错。第二，这一点是iOS面试当中经常面到的问题：如何给扩展添加属性？。
Teacher: What's your Chinese name?
XiaoMing: I have no one.
LiHua: You should have one.
LiHua: Your Chinese name is __
在程序当中，假设XiaoMing的中没有chineseName这个属性，后来被Runtime添加一个名字叫chineseName的属性。那么，Runtime是如何做到的呢？
①申明chineseName属性
#import "XiaoMing.h"
@interface XiaoMing (MutipleName)
@property(nonatomic,copy) NSString *chineseName;
@end
②动态添加属性和实现方法
#import "XiaoMing+MutipleName.h"
#import
@implementation XiaoMing (MutipleName)
char cName;
-(void)setChineseName:(NSString *) chineseName{
objc_setAssociatedObject(self, &cName, chineseName, OBJC_ASSOCIATION_COPY_NONATOMIC);
}
-(NSString *)chineseName{
return objc_getAssociatedObject(self, &cName);
}
@end
③使用chineseName属性
-(void)answer{
NSLog(@"My Chinese name is %@",self.xiaoMing.chineseName);
self.chineseNameTf.text = self.xiaoMing.chineseName;
}
