instantiated class is nil when called inside viewdidload() - ios

Question

I am trying to learn the VIPER architecture model and one thing I can't figure out is when I do the following:
Instantiate promotionPresenter class
Instantiate promotionsViewController
assign promotionsViewController.presenter = (instantiated promotionPresenter class from step 1)
try to access the instantiated presenter class from inside viewdidload() function within promotionviewController class.
presenter is nil.
Why is presenter nil? I already instantiated it.
import UIKit
/*
* The Router responsible for navigation between modules.
*/
class PromotionsWireframe : PromotionsWireframeInput {
// Reference to the ViewController (weak to avoid retain cycle).
var promotionsViewController: PromotionsViewController!
var promotionsPresenter: PromotionsPresenter!
var rootWireframe: RootWireframe!
init() {
let promotionsInteractor = PromotionsInteractor()
// Presenter is instantiated
promotionsPresenter = PromotionsPresenter()
promotionsPresenter.interactor = promotionsInteractor
promotionsPresenter.wireframe = self
promotionsInteractor.output = promotionsPresenter
}
func presentPromotionsIntefaceFromWindow(_ window: UIWindow) {
//view controller is instantiated
promotionsViewController = promotionsViewControllerFromStoryboard()
//presenter of view controller is assigned to instantiaed class
promotionsViewController.presenter = promotionsPresenter
promotionsPresenter.view = promotionsViewController
}
private func promotionsViewControllerFromStoryboard() -> PromotionsViewController {
let storyboard = UIStoryboard(name: "PromotionsStoryboard", bundle: nil )
let viewController = storyboard.instantiateViewController(withIdentifier: "promotionsViewController") as! PromotionsViewController
return viewController
}
}
import UIKit
class PromotionsViewController : UIViewController, PromotionsViewInterface {
// Reference to the Presenter's interface.
var presenter: PromotionsModuleInterface!
var promotions: [Promotion]!
/*
* Once the view is loaded, it sends a command
* to the presenter asking it to update the UI.
*/
override func viewDidLoad() {
super.viewDidLoad()
// getting error because presenter is unwrapped as nil
self.presenter.updateView()
}
func showPromotionsData(_ promotions: [Promotion]) {
// need to implement
}
}
import Foundation
class PromotionsPresenter : PromotionsModuleInterface, PromotionsInteractorOutput {
// Reference to the View (weak to avoid retain cycle).
var view: PromotionsViewInterface!
// Reference to the Interactor's interface.
var interactor: PromotionsInteractorInput!
var wireframe: PromotionsWireframe!
func updateView() {
self.interactor.fetchLocalPromotions()
}
func PromotionsFetched(_promotions: [Promotion]) {
// need to implement
}
}

Answer 1

I suggest you take this boilerplate (https://github.com/CheesecakeLabs/Boilerplate_iOS_VIPER) and read this post (https://www.ckl.io/blog/best-practices-viper-architecture/) in order to learn not only how to correctly initialize your VIPER modules, but also how to automate VIPER files creation and initiazlization