Swift implementation of idea that manny view controller can do light work: http://khanlou.com/2016/02/many-controllers/

ViewControllerLifecycleBehavior.swift

public protocol ViewControllerLifecycleBehavior {
    func afterLoading(_ viewController: UIViewController)

    func beforeAppearing(_ viewController: UIViewController)

    func afterAppearing(_ viewController: UIViewController)

    func beforeDisappearing(_ viewController: UIViewController)

    func afterDisappearing(_ viewController: UIViewController)

    func beforeLayingOutSubviews(_ viewController: UIViewController)

    func afterLayingOutSubviews(_ viewController: UIViewController)
}

extension ViewControllerLifecycleBehavior {
    public func afterLoading(_ viewController: UIViewController) {}

    public func beforeAppearing(_ viewController: UIViewController) {}

    public func afterAppearing(_ viewController: UIViewController) {}

    public func beforeDisappearing(_ viewController: UIViewController) {}

    public func afterDisappearing(_ viewController: UIViewController) {}

    public func beforeLayingOutSubviews(_ viewController: UIViewController) {}

    public func afterLayingOutSubviews(_ viewController: UIViewController) {}
}

public extension UIViewController {
    /*
     Add behaviors to be hooked into this view controller’s lifecycle.

     This method requires the view controller’s view to be loaded, so it’s best to call
     in `viewDidLoad` to avoid it being loaded prematurely.

     - parameter behaviors: Behaviors to be added.
     */

    public func add(behaviors: [ViewControllerLifecycleBehavior]) {
        let behaviorViewController = LifecycleBehaviorViewController(behaviors: behaviors, behaviorsHost: self)
        self.add(behaviorViewController: behaviorViewController)
    }

    private func add(behaviorViewController: LifecycleBehaviorViewController) {
        self.addChildViewController(behaviorViewController)
        self.view.addSubview(behaviorViewController.view)
        behaviorViewController.didMove(toParentViewController: self)
    }
}

fileprivate final class LifecycleBehaviorViewController: UIViewController {
    private unowned let behaviorsHost: UIViewController
    private let behaviors: [ViewControllerLifecycleBehavior]

    // MARK: - Initialization

    init(behaviors: [ViewControllerLifecycleBehavior], behaviorsHost: UIViewController) {
        self.behaviorsHost = behaviorsHost
        self.behaviors = behaviors

        super.init(nibName: nil, bundle: nil)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    // MARK: - UIViewController

    override func viewDidLoad() {
        super.viewDidLoad()

        view.isHidden = true

        for behavior in self.behaviors {
            behavior.afterLoading(self.behaviorsHost)
        }
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        for behavior in self.behaviors {
            behavior.beforeAppearing(self.behaviorsHost)
        }
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        for behavior in self.behaviors {
            behavior.afterAppearing(self.behaviorsHost)
        }
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)

        for behavior in self.behaviors {
            behavior.beforeDisappearing(self.behaviorsHost)
        }
    }

    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)

        for behavior in self.behaviors {
            behavior.afterDisappearing(self.behaviorsHost)
        }
    }

    override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()

        for behavior in self.behaviors {
            behavior.beforeLayingOutSubviews(self.behaviorsHost)
        }
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()

        for behavior in self.behaviors {
            behavior.afterLayingOutSubviews(self.behaviorsHost)
        }
    }
}