试图追查为什么我从一个视图到另一个视图取回 Nil 数据

Question

I have two view controllers both views are holding an integer of data from the textfield and that data I would like to be saved and or held so I can error check against that number on the next view. The issue is my data is always nil. If someone can shed some insight on why this is the case I would greatly appreciate it. Code below.

Thanks to Keshu the answer has been solved. I put the Code below in the else statement and works perfectly.

gameInfo(player: yourdata, numberPicked: yourdata, datePlayed: yourdata, winner: yourdata, turn: yourdata) 

First view

class PlayerSelectViewController: UIViewController {

@IBOutlet weak var playerButton: UIButton!
@IBOutlet weak var playersTextBox: UITextField!

var gameInfo:GameInfo?

override func viewDidLoad() {
    super.viewDidLoad()


}

@IBAction func cancelBtnClicked(_ sender: Any) {
    self.navigationController?.popToRootViewController(animated: true)
}


@IBAction func okBtnClicked(_ sender: Any) {
    guard let playerTotal = Int(playersTextBox.text!) else {
        makeAlert(title: "Enter a Number", message: "Please enter a number and then press Ok")
        return
    }
    if playerTotal < 2 {
        makeAlert(title: "Incorrect Number", message: "Please input more than \(playersTextBox.text!)")
    } else if playerTotal > 50 {
        makeAlert(title: "Incorrect Number", message: "Please input less than \(playersTextBox.text!)")
    } else {
        gameInfo?.player = playerTotal
    }
}

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    let serverController = segue.destination as! ServerSelectViewController
    serverController.gameInfo = gameInfo
}


func makeAlert (title: String, message: String) {
    let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertController.Style.alert)

    alert.addAction(UIAlertAction(title: "Ok", style: UIAlertAction.Style.default, handler: {(action) in
        alert.dismiss(animated: true, completion: nil)}))
    self.present(alert, animated: true, completion: nil)
}

Second view

    @IBOutlet weak var serverTextBox: UITextField!
@IBOutlet weak var serverButton: UIButton!

var gameInfo:GameInfo?

override func viewDidLoad() {
    super.viewDidLoad()
    print(gameInfo?.player as Any)
}

@IBAction func cancelBtnClicked(_ sender: Any) {
    self.navigationController?.popToRootViewController(animated: true)
}

@IBAction func okBtnClicked(_ sender: Any) {
    guard let number = Int(serverTextBox.text!) else {
        makeAlert(title: "Enter a Number", message: "Please enter a number and then press Ok")
        return
    }
    if number < 1 {
        makeAlert(title: "Incorrect Number", message: "Please input more than \(serverTextBox.text!)")
    } else if number > 1000 {
        makeAlert(title: "Incorrect Number", message: "Please input less than \(serverTextBox.text!)")
    } else {
        gameInfo?.numberPicked = number
    }
}


func makeAlert (title: String, message: String) {
    let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertController.Style.alert)
    alert.addAction(UIAlertAction(title: "Ok", style: UIAlertAction.Style.default, handler: {(action) in
    alert.dismiss(animated: true, completion: nil)}))

    self.present(alert, animated: true, completion: nil)
}

Model

class GameInfo: Codable {
var player: Int
var numberPicked: Int
var datePlayed: Date
var winner: String
var turn: Int

init(player: Int, numberPicked: Int, datePlayed: Date, winner: String, turn: Int) {
    self.player = player
    self.numberPicked = numberPicked
    self.datePlayed = datePlayed
    self.winner = winner
    self.turn = turn
}


static func loadGameInfo() -> [GameInfo] {
    return []
}


static let documentsDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!

static let archiveURL = documentsDirectory.appendingPathComponent("gameInformation").appendingPathExtension("plist")

static func saveToFile(gameInformation: [GameInfo]) {
    let propertyListEncoder = PropertyListEncoder()
    let gameInfo = try? propertyListEncoder.encode(gameInformation)

    try? gameInfo?.write(to: archiveURL, options: .noFileProtection)
}

static func loadFromFile() -> [GameInfo]? {
    guard let gameInfo = try? Data(contentsOf: archiveURL) else { return nil }

    let propertyListDecoder = PropertyListDecoder()

    return try? propertyListDecoder.decode(Array<GameInfo>.self, from: gameInfo)

}

Answer 1

The issue is that you have created a segue from your button to your next view controller. So by the time your okBtnClicked action is called, you are on your next view controller and so the data is nil.

Remove the segue from your button and make it from your ViewController 1 to ViewController2. And then in your okBtnClicked function, performSegue at the end.

@IBAction func okBtnClicked(_ sender: Any) {
guard let number = Int(serverTextBox.text!) else {
    makeAlert(title: "Enter a Number", message: "Please enter a number and then press Ok")
    return
}
if number < 1 {
    makeAlert(title: "Incorrect Number", message: "Please input more than \(serverTextBox.text!)")
} else if number > 1000 {
    makeAlert(title: "Incorrect Number", message: "Please input less than \(serverTextBox.text!)")
} else {
    gameInfo = GameInfo(player: number, numberPicked: 0, datePlayed: Date(), winner:"", turn: 0)
}
self.performSegue(withIdentifier: "yourSegueIdentifier", sender: self)
}