无法获取另一个类中 var 的值

Question

我正在尝试从另一个类中获取 String var 的值，但是当我在新类上使用它时，该值是空的。 我有 MainViewController.swift 类：

    var movieIDSelected = String()

@IBAction func tapPosterButton(_ sender: UIButton) {
    switch sender.tag
    {
    case 101: movieIDSelected = theaterMovieID[0]
    print(movieIDSelected) //The value isn't empty
        break
    }
  }

第二个 MovieViewController.swift 类：

var HomeView = ViewPop()

override func viewDidLoad() {
    super.viewDidLoad()

    let movieID = HomeView.movieIDSelected
    print(movieID) //The value is empty
}

Answer 1

用你当前的代码在 MainVC 中试试这个

if let home = UIApplication.shared.keyWindow?.rootViewController as? ViewPop {
   print("home exists ",home.movieIDSelected)
}

//

但是你应该只有一个到destinationVC的segue并将它链接到VC而不是每个按钮的segue，然后在按钮操作中实现prepareForSegue并触发performSegue以进行segue

//

@IBAction func tapPosterButton(_ sender: UIButton) {
    switch sender.tag
    {
       case 101: movieIDSelected = theaterMovieID[0]
        print(movieIDSelected) //The value isn't empty
        self.performSegue(withIdentifier: "goToNext", sender:1)

        break
    }
}

//

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

      let des = segue.destination as! MovieViewController

      des.sendedValue = self.movieIDSelected

      des.buttonNumber = sender as! Int

}

//

class MovieViewController : UIViewController {

     var sendedValue = ""

    var buttonNumber = 0 // default value won't affect 
}