ConstructorExample1.swift

/// Does something special that ViewController_A wants
struct Service_A {
    func doSomething() {
    }
}

/// Does something special that ViewController_B wants
struct Service_B {
    func doSomething() {
    }
}

/// Does something special that ViewController_C wants
struct Service_C {
    func doSomething() {
    }
}

/// Does something special that ViewController_D wants
struct Service_D {
    func doSomething() {
    }
}


class ViewController : UIViewController {
    init() {
        super.init(nibName: nil, bundle: nil)
    }
    /// make it so we can have a simple example w/o stupid constructors
    @available(*, unavailable)
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

/// Responsible for calling serviceA then presenting ViewController_B
class ViewController_A : ViewController {
    let serviceA: Service_A
    let serviceB: Service_B
    let serviceC: Service_C
    let serviceD: Service_D

    init(
        serviceA: Service_A,
        serviceB: Service_B,
        serviceC: Service_C,
        serviceD: Service_D
        ) {
        self.serviceA = serviceA
        self.serviceB = serviceB
        self.serviceC = serviceC
        self.serviceD = serviceD
        super.init()
    }

    func showNestedViewController() {
        serviceA.doSomething()
        presentViewController(
            ViewController_B(
                serviceB: serviceB,
                serviceC: serviceC,
                serviceD: serviceD
            ),
            animated: true,
            completion: nil
        )
    }
}

/// Responsible for calling serviceB then presenting ViewController_C
class ViewController_B : ViewController {
    let serviceB: Service_B
    let serviceC: Service_C
    let serviceD: Service_D

    init(
        serviceB: Service_B,
        serviceC: Service_C,
        serviceD: Service_D
        ) {
        self.serviceB = serviceB
        self.serviceC = serviceC
        self.serviceD = serviceD
        super.init()
    }

    func showNestedViewController() {
        serviceB.doSomething()
        presentViewController(
            ViewController_C(
                serviceC: serviceC,
                serviceD: serviceD
            ),
            animated: true,
            completion: nil
        )
    }
}



/// Responsible for calling serviceC then presenting ViewController_D
class ViewController_C : ViewController {
    let serviceC: Service_C
    let serviceD: Service_D

    init(
        serviceC: Service_C,
        serviceD: Service_D
        ) {
        self.serviceC = serviceC
        self.serviceD = serviceD
        super.init()
    }

    func showNestedViewController() {
        serviceC.doSomething()
        presentViewController(
            ViewController_D(
                serviceD: serviceD
            ),
            animated: true,
            completion: nil
        )
    }
}


/// Responsible for calling serviceC then presenting ViewController_D
class ViewController_D : ViewController {
    let serviceD: Service_D

    init(
        serviceD: Service_D
        ) {
        self.serviceD = serviceD
        super.init()
    }


    func doSomething() {
        serviceD.doSomething()
    }
}