方法交换的作用：
一、在不修改源代码的基础上，对方法内的代码进行修改
二、
- (void)viewDidLoad {
[super viewDidLoad];
objc_msgSend(self,@selector(test));
[self say];
[self mySay];
[self changeMethod];
[self say];
[self mySay];
}
- (void)test
{
NSLog(@"test");
}
- (void)changeMethod
{
/*
class_getInstanceMethod 得到类的实例方法
class_getClassMethod 得到类的类方法
*/
Method say1 = class_getInstanceMethod([ViewController class], @selector(say));
Method mySay1 = class_getInstanceMethod([ViewController class], @selector(mySay));
method_exchangeImplementations(say1, mySay1);
}
- (void)say
{
NSLog(@"%s",__FUNCTION__);
}
- (void)mySay
{
NSLog(@"%s",__FUNCTION__);
}
测试结果：
2016-08-11 16:17:16.997 RuntimeTest[3199:126416] test
2016-08-11 16:17:16.997 RuntimeTest[3199:126416] - [ViewController say]
2016-08-11 16:17:16.997 RuntimeTest[3199:126416] - [ViewController mySay]
2016-08-11 16:17:16.998 RuntimeTest[3199:126416] -[ViewController mySay]
2016-08-11 16:17:16.998 RuntimeTest[3199:126416] -[ViewController say]