App開啟後指定第一個ViewController

app打開後，要指定第一個view controller有兩種方法。
一種是寫code：

class AppDelegate: UIApplicationDelegate{
  func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    if self.window?.rootViewController == nil{
       let loginStoryboard = UIStoryboard(name: "xxx", bundle: nil)
       let launchVC = loginStoryboard.instantiateViewController(withIdentifier: "LaunchVC") as! LaunchViewController
       self.window?.rootViewController = launchVC
    }
  }
}

另外一種是直接在View Conroller上做設定，將is Initial View Controller勾起來即可：