1. 动态的添加对象的成员变量和方法

1. 动态变量控制

1）Sense：

Teacher: What's your name?

XiaoMing: My name is XiaoMing.

Teacher: Pardon?

XiaoMing: My name is __

在程序当中，假设XiaoMing的name原来的值为XiaoMing，后来被Runtime偷换了一个名字叫Minggo。那么，Runtime是如何做到的呢？

2）Step：

①动态获取XiaoMing类中的所有属性[当然包括私有]

Ivar *ivar = class_copyIvarList([self.xiaoMing class], &count);

②遍历属性找到对应name字段

const char *varName = ivar_getName(var);

③修改对应的字段值成Minggo

object_setIvar(self.xiaoMing, var, @"Minggo");

3）Show Code：

-(void)answer{

     unsigned int count = 0;

     Ivar *ivar = class_copyIvarList([self.xiaoMing class], &count);

     for (int i = 0; i<count; i++){

           Ivar var = ivar[i];

           const char *varName = ivar_getName(var);

           NSString *name = [NSString stringWithUTF8String:varName];

           if ([name isEqualToString:@"_englishName"]) {

                       object_setIvar(self.xiaoMing, var, @"Minggo");

                       break;

              }

     }

     NSLog(@"XiaoMing first answer is %@",self.xiaoMing.englishName);

     self.nameTf.text = self.xiaoMing.englishName;

}