Navigation-LoopingHandler.swift

class LoginViewController: UIViewController {
	
	...
	@IBAction func signUpButtonTapped(sender: UIButton) {
		let viewController = RegisterViewController()
		self.navigationController?.pushViewController(viewController, animated: true)
	}
	
	func backToPreviousScreen() {
		self.navigationController?.popToRootViewControllerAnimated(true)
	}
	...
	
}

internal class RegisterViewController: UIViewController {
	
	...
	@IBAction func pushLoginPage(sender: AnyObject) {
		let viewController = LoginViewController()
		self.navigationController?.pushViewController(viewController, animated: true)
	}
	
	func backToPreviousScreen() {
		self.navigationController?.popToRootViewControllerAnimated(true)
	}
	...

}