ios runtime系列 method_exchangeImplementations方法

- (void)viewDidLoad
{
[super viewDidLoad];

Method m1 = class_getInstanceMethod([self class], @selector(method1));

Method m2 = class_getInstanceMethod([self class], @selector(method2));

[self method1];

[self method2];

method_exchangeImplementations(m1, m2);

[self method1];

[self method2];
}

- (void)method1
{
NSLog(@"%s", __func__);
}
- (void)method2
{
NSLog(@"%s", __func__);
}