从StoryBoard加载控制器

1.创建窗口
self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
2.加载控制器
从StoryBoard当中加载控制器
UIStoryboard *storyBoard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
加载剪头指向的控制器
UIViewController *vc = [storyBoard instantiateInitialViewController];

3.设置窗口根控制器
self.window.rootViewController = vc;
4.显示窗口
[self.window makeKeyAndVisible];

加载控制器的两种方式
0.加载指定的StoryBoard.
UIStoryboard *storyBoard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
1.加载箭头所指向的控制器.
UIViewController *vc = [storyBoard instantiateInitialViewController];
2.加载指定标识的控制器.
UIViewController *vc = [storyBoard instantiateViewControllerWithIdentifier:@"VCStoryBoardID"];