当控制器的view即将显示时调用

 -(void)viewWillAppear:(BOOL)animated{
   [super viewWillAppear:animated];
 }

当控制器的view已经显示完毕调用

 - (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
 }

当控制器的view加载完毕调用

- (void)viewDidLoad {
   [super viewDidLoad];
}

当控制器的view即将消失时调用

- (void)viewWillDisappear:(BOOL)animated {
  [super viewWillDisappear:animated];
}

当控制器的view已经消失完毕调用

- (void)viewDidDisappear:(BOOL)animated {
   [super viewDidDisappear:animated];
}

跟内存相关

当控制器view即将要卸载时调用

- (void)viewWillUnload {
[super viewWillUnload];
}

当控制器view卸载完毕时调用

- (void)viewDidUnload {
[super viewDidUnload];
}

当控制器收到内存警告时调用

- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
}