ios - 无法将类型 'MyAppName.ProfileController' 的值转换为 'MyAppName.SelectController'

Question

我有一个带有 3 个按钮和一个步进器的 viewController

import UIKit
import AVFoundation

class HomeController: UIViewController {
    var steppers : UIStepper?

    static var globalLimit: Int = 0

    @IBOutlet weak var hourLabel: UILabel!
    @IBOutlet weak var stepper: UIStepper!

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if let vc : SelectController = (segue.destination as? SelectController)! {
            vc.limit = Int(stepper.value)
            HomeController.globalLimit = Int(stepper.value)
        }
        if let np = segue.destination as? CourseController {
            np.numberPlaces = Int(stepper.value)
        }
    }

我的应用程序在这里崩溃了:

if let vc : SelectController = (segue.destination as? SelectController)!

错误:

Could not cast value of type 'MyAppName.ProfileController' to 'MyAppName.SelectController'

之后，当我按下一个不是 SelectTapped 按钮的按钮时(在本例中我按下了配置文件按钮)。问题的原因是什么？我该如何解决？我预计有必要使用static var globalLimit。

Answer 1

您正在强制转换并会产生错误。更改方法如下:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

    if let vc = segue.destination as? SelectController {
        vc.limit = Int(stepper.value)
        HomeController.globalLimit = Int(stepper.value)
    }
    if let np = segue.destination as? CourseController {
        np.numberPlaces = Int(stepper.value)
    }

}