在 viewdidload() 内部调用时实例化的类为 nil

Question

我正在尝试学习 VIPER 架构模型，但我无法弄清楚的一件事是当我执行以下操作时：

1. 实例化promotionPresenter类
2. 实例化promotionsViewController
3. assign PromotionsViewController.presenter =（第 1 步中实例化的promotionPresenter 类）
4. 尝试从promotionviewController 类中的viewdidload() 函数内部访问实例化的presenter 类。
5. 演示者为零。 为什么主持人是零？我已经实例化了它。

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

我建议您阅读此样板文件 (https://github.com/CheesecakeLabs/Boilerplate_iOS_VIPER) 并阅读这篇文章 (https://www.ckl.io/blog/best-practices-viper-architecture/)，以便不仅了解如何正确初始化您的 VIPER 模块，还了解如何自动创建和初始化 VIPER 文件