UIViewController的创建、加载和卸载

一. UIViewController的创建和初始化

        1. 通过NIB文件初始化

        [ [UIViewController alloc] initWithNibName:nibName bundle:nibBundle];

        - (id)initWithNibName:(NSString *)nibName bundle:(NSBundle *)nibBundle;

        2. 通过UIStoryboard初始化

              - (id)instantiateViewControllerWithIdentifier:(NSString *)identifier;

        3. 重载loadView方法

         self.view = [ [UIView alloc] initWithFrame: aRect];

二.  加载视图  loadView->viewDidLoad->viewWillAppear->viewWillLayoutSubviews->viewDidLayoutSubviews->viewDidAppear

       - (void)loadView;                    注：NIB文件中若关联了view，则不用重载该方法

       - (void)viewDidLoad;

       - (void)viewWillAppear:(BOOL) animated;

       - (void)viewWillLayoutSubviews;

       - (void)viewDidLayoutSubviews;

       - (void)viewDidAppear:(BOOL) animated;

三. 卸载视图 viewWillDisappear->viewDidDisappear->dealloc

      - (void)viewWillDisappear:(BOOL)animated;

      - (void)viewDidDisappear:(BOOL)animated;

      - (void)dealloc;