- (void)beginAppearanceTransition:(BOOL)isAppearing animated:(BOOL)animated __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_5_0);

- (void)endAppearanceTransition __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_5_0);

 今天看别人代码，用到这两个函数，这两个函数的是成对出现的，基本用法为

[self beginAppearanceTransition:YES animated:NO];//调用viewWillAppear

 [self  endAppearanceTransition];//调用viewDidAppear

[self beginAppearanceTransition:NO animated:NO];//调用viewWillDisappear

beginAppearanceTransition