Learn from 斯坦福大学公开课:iOS 8开发
Build by self for the test for the multi mvc, segue and popover
Build with Xcode 9.4.1 and Swift 4.1
Knowledge point:
//处理不同指向 override func prepare(for segue: UIStoryboardSegue, sender: Any?) {}
//本地缓存 UserDefaults.standard
//自适应 textView.sizeThatFits(presentingViewController!.view.bounds.size)
//更改popover在iPhone上的全屏 UIPopoverPresentationControllerDelegate