ios controller的调用方法的周期
+(void)load;
+(void)initialize;
-(id)initwith...;
-(void)loadview;
-(void)viewDidLoad;
-(void)viewWillAppear:(BOOL)animated;
-(void)viewDidAppear:(BOOL)animated;
-(void)viewWillDisappear:(BOOL)animated;
-(void)viewDidDisappear:(BOOL)animated;
这是controller的调用顺序;