Example 2

import Foundation
import UIKit
import XCTest

enum AuthType {
    case login
    case signUp
}


protocol AuthViewFactory {

    static func authView(for type: AuthType) -> AuthView
    static func authController(for type: AuthType) -> AuthViewController
}

class StudentAuthViewFactory: AuthViewFactory {

    static func authView(for type: AuthType) -> AuthView {
        print("Student View has been created")
        switch type {
            case .login: return StudentLoginView()
            case .signUp: return StudentSignUpView()
        }
    }

    static func authController(for type: AuthType) -> AuthViewController {
        let controller = StudentAuthViewController(contentView: authView(for: type))
        print("Student View Controller has been created")
        return controller
    }
}

class TeacherAuthViewFactory: AuthViewFactory {

    static func authView(for type: AuthType) -> AuthView {
        print("Teacher View has been created")
        switch type {
            case .login: return TeacherLoginView()
            case .signUp: return TeacherSignUpView()
        }
    }

    static func authController(for type: AuthType) -> AuthViewController {
        let controller = TeacherAuthViewController(contentView: authView(for: type))
        print("Teacher View Controller has been created")
        return controller
    }
}



protocol AuthView {

    typealias AuthAction = (AuthType) -> ()

    var contentView: UIView { get }
    var authHandler: AuthAction? { get set }

    var description: String { get }
}

class StudentSignUpView: UIView, AuthView {

    private class StudentSignUpContentView: UIView {

        /// This view contains a number of features available only during a
        /// STUDENT authorization.
    }

    var contentView: UIView = StudentSignUpContentView()

    /// The handler will be connected for actions of buttons of this view.
    var authHandler: AuthView.AuthAction?

    override var description: String {
        return "Student-SignUp-View"
    }
}

class StudentLoginView: UIView, AuthView {

    private let emailField = UITextField()
    private let passwordField = UITextField()
    private let signUpButton = UIButton()

    var contentView: UIView {
        return self
    }

    /// The handler will be connected for actions of buttons of this view.
    var authHandler: AuthView.AuthAction?

    override var description: String {
        return "Student-Login-View"
    }
}



class TeacherSignUpView: UIView, AuthView {

    class TeacherSignUpContentView: UIView {

        /// This view contains a number of features available only during a
        /// TEACHER authorization.
    }

    var contentView: UIView = TeacherSignUpContentView()

    /// The handler will be connected for actions of buttons of this view.
    var authHandler: AuthView.AuthAction?

    override var description: String {
        return "Teacher-SignUp-View"
    }
}

class TeacherLoginView: UIView, AuthView {

    private let emailField = UITextField()
    private let passwordField = UITextField()
    private let loginButton = UIButton()
    private let forgotPasswordButton = UIButton()

    var contentView: UIView {
        return self
    }

    /// The handler will be connected for actions of buttons of this view.
    var authHandler: AuthView.AuthAction?

    override var description: String {
        return "Teacher-Login-View"
    }
}



class AuthViewController: UIViewController {

    fileprivate var contentView: AuthView

    init(contentView: AuthView) {
        self.contentView = contentView
        super.init(nibName: nil, bundle: nil)
    }

    required convenience init?(coder aDecoder: NSCoder) {
        return nil
    }
}

class StudentAuthViewController: AuthViewController {

    /// Student-oriented features
}

class TeacherAuthViewController: AuthViewController {

    /// Teacher-oriented features
}


private class ClientCode {

    private var currentController: AuthViewController?

    private lazy var navigationController: UINavigationController = {
        guard let vc = currentController else { return UINavigationController() }
        return UINavigationController(rootViewController: vc)
    }()

    private let factoryType: AuthViewFactory.Type

    init(factoryType: AuthViewFactory.Type) {
        self.factoryType = factoryType
    }

    /// MARK: - Presentation

    func presentLogin() {
        let controller = factoryType.authController(for: .login)
        navigationController.pushViewController(controller, animated: true)
    }

    func presentSignUp() {
        let controller = factoryType.authController(for: .signUp)
        navigationController.pushViewController(controller, animated: true)
    }

    /// Other methods...
}


class AbstractFactoryRealWorld: XCTestCase {

    func testFactoryMethodRealWorld() {

        #if teacherMode
            let clientCode = ClientCode(factoryType: TeacherAuthViewFactory.self)
        #else
            let clientCode = ClientCode(factoryType: StudentAuthViewFactory.self)
        #endif

        /// Present LogIn flow
        clientCode.presentLogin()
        print("Login screen has been presented")

        /// Present SignUp flow
        clientCode.presentSignUp()
        print("Sign up screen has been presented")
    }
}

Teacher View has been created
Teacher View Controller has been created
Login screen has been presented
Teacher View has been created
Teacher View Controller has been created
Sign up screen has been presented