Content view controllers：管理内容
Container view controllers ：从其他的view controllers（child view controllers） 收集信息并呈现
－－－－UINavigationController, UISplitViewController, and UIPageViewController.
1、The Role of View Controllers
管理视图、数据封送、交互、free memory管理、自动调节
2、View Controller Programming Guide for iOS
介绍视图控制器在IOS上的设计模式和通用用途。
3、App Programming Guide for iOS
介绍其开发过程,并描述核心架构。
4、App Distribution Guide
描述配置的步骤,编译、调试和调优应用程序并提交其App Store。
a framework: a dictionary 包含了动态共享库和资源
a dynamic shared library and the resources
Presenting a View Controller
Presenting a view controller creates a relationship between the original view controller, known as the presenting view controller, and the new view controller to be displayed, known as the presented view controller.
The Presentation and Transition Process
1--Presentation Styles
Full-Screen Presentation Styles
The Popover Style
The Current Context Styles
Custom Presentation Styles
Transition Styles
Presenting 与 Showing a View Controller
presentViewController:animated:completion:
showViewController:sender: 和 showDetailViewController:sender:
1、UIViewControllerInteractiveTransitioning
2、UIViewControllerAnimatedTransitioning
3、UIViewControllerContextTransitioning：实现自定义视图控制器的动画过渡。
