Starts the application without storyboard, using navBar and tabBar

application.swift

// in AppDelegate.swift
private func setupApplicationController() {
  window = UIWindow()
  window?.makeKeyAndVisible()

  let vc = UINavigationController(rootViewController: MainController())
  window?.rootViewController = vc
}

private func setupApplicationAppearance() {
  // navBar colors
  UINavigationBar.appearance().barTintColor = .red
  UINavigationBar.appearance().tintColor = .white

  // tabBar colors
  UITabBar.appearance().barTintColor = .red
  UITabBar.appearance().tintColor = .white
}