实例化类在viewdidload()内部调用时为nil

Question

我正在尝试学习VIPER体系结构模型，但有一件事我无法理解，那就是当我执行以下操作时：

1. 实例化promotionPPresenter类
2. 实例化promotionsViewController
3. assign promotionViewController.prepreser=(步骤1中实例化的promotionPresenter类)
4. 尝试从promotionviewController类中的viewdidload()函数内部访问实例化的演示者类
5. 演讲者为零。为什么演示者为零？我已经实例化了

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

我建议你拿这个样板(https://github.com/CheesecakeLabs/Boilerplate_iOS_VIPER)并阅读这篇文章(https://www.ckl.io/blog/best-practices-viper-architecture/)为了不仅学习如何正确初始化VIPER模块，还学习如何自动化VIPER文件的创建和初始化