简介
总结下页面跳转时的回调时机，viewWillAppear、viewDidAppear、viewWillDisappear、viewDidDisappear 这4个方法调用时机。
页面跳转有2种方式，push和present。push和pop对应，present和dismiss对应
push pop跳转
A页面跳B页面
跳转
A viewWillDisappear
B viewWillAppear
A viewDidDisappear
B viewDidAppear
返回
B viewWillDisappear
A viewWillAppear
B viewDidDisappear
A viewDidAppearpresent dismiss跳转
跳转
A viewWillDisappear
B viewWillAppear
B viewDidAppear
A viewDidDisappear
返回
B viewWillDisappear
A viewWillAppear
A viewDidAppear
B viewDidDisappear总结
可以看出跳转的时候都是先调will方法后掉did方法，push和present的区别，在于A viewDidDisappear 和 B viewDidAppear的顺序，push的时候是B viewDidDisappear先调，present是B viewDidAppear先调用