Teacher: What's your name?
XiaoMing: My name is XiaoMing.
Teacher: Pardon?
XiaoMing: My name is __
在程序当中，假设XiaoMing的第一次回答为firstSay，后来被Runtime交换了一个名字叫secondSay的方法，最终再调用firstSay的时候，其实是调用了secondSay的实现。那么，Runtime是如何做到的呢？
①动态找到firstSay和secondSay方法
Method m1 = class_getInstanceMethod([self.xiaoMing class], @selector(firstSay));
Method m2 = class_getInstanceMethod([self.xiaoMing class], @selector(secondSay));
②交换两个方法
method_exchangeImplementations(m1, m2);
-(void)answer{
Method m1 = class_getInstanceMethod([self.xiaoMing class], @selector(firstSay));
Method m2 = class_getInstanceMethod([self.xiaoMing class], @selector(secondSay));
method_exchangeImplementations(m1, m2);
NSString *secondName = [self.xiaoMing firstSay];
self.nameTf.text = secondName;
NSLog(@"XiaoMing:My name is %@",secondName);
}
