最近iPhoneアプリの開発を始めてみて、最初に画面遷移するだけでとてもハマったのでメモしておく。
個人的にiPhoneの画面遷移って鬼門な気がしてる。Androidは簡単なのに...

画面遷移いろいろ

同じStoryboard のViewControllerへ

let next = self.storyboard!.instantiateViewController(withIdentifier: "Next1ViewController")
self.present(next, animated: true)

別のStoryboardのViewControllerへ

let storyboard = UIStoryboard(name: "Next", bundle: nil)
let next = storyboard.instantiateViewController(withIdentifier: "Next2ViewController")
self.present(next, animated: true)

NavigationControllerのあるStoryboardへ

let storyboard = UIStoryboard(name: "Navi", bundle: nil)
let next = storyboard.instantiateViewController(withIdentifier: "Next3ViewController")
self.present(next, animated: true)

NavigationControllerを持つViewControllerでNavigationControllerを使って画面遷移

let next = self.storyboard?.instantiateViewController(withIdentifier: "Next4ViewController") 
self.navigationController?.pushViewController(next!, animated: true)

TabbarControllerのあるStoryboardへ

let storyboard = UIStoryboard(name: "Tab", bundle: nil)
let next = storyboard.instantiateViewController(withIdentifier: "Next5ViewController")
self.present(next, animated: true)

TabbarControllerを持つViewControllerでTabbarControllerを使って画面遷移

※Storyboard上でAttribute InspectorでBarItemのtagに番号つけておく

self.tabBarController?.selectedIndex = 1

rootViewControllerを直接入れ替える

let storyboard = UIStoryboard(name: "Tab", bundle: nil)
let next = storyboard.instantiateViewController(withIdentifier: "Next5ViewController")
let appdelegate = UIApplication.shared.delegate as! AppDelegate
appdelegate.window?.rootViewController = next

たぶんこれくらい知ってれば大丈夫なはず。。。