在Swift视图控制器之间传递数据不起作用的第一个Segue过渡

Question

我有一个Swift文件，其中包含四个独立的元组数组。 在ViewControllerA中，我有四个不同的按钮，每个按钮都会更改“ selectedPosition”的值，并设置为触发“ SegueAtoB”。 然后应在ViewControllerB中使用“ selectedPosition”来选择适当的数组，以在ViewControllerB上填充UIPickerView。

当前，我的“准备segue”方法仅在第二次按下按钮时才传递正确的数据，例如，当应用程序加载到ViewControllerA中时，我按下一个按钮，它将带我到ViewControllerB，但是为UIPickerView选择的数组是默认的，当我退回到ViewControllerA并按一个按钮，代码按预期工作。

ViewControllerA：

class ViewControllerA: UIViewController {

    // Variable to hold position selected (passed through to ViewControllerB)
    var selectedPosition : String = ""


    // Button1
    // Set up to run "SegueAtoB"
    @IBOutlet weak var selectButton_CEO: UIButton!
    @IBAction func selectButton_CEO_Tapped(_ sender: UIButton) {
        selectedPosition = "CEO"
    }


    // MARK: - Navigation
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "SegueAtoB" {
            let VC : ViewControllerB = segue.destination as! ViewControllerB
            VC.ReceivePlayerDataDelegate = self
            VC.currentPosition = selectedPosition
        }
    }

}

ViewControllerB：

class ViewControllerB: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate {


    // set the position passed through from ViewControllerB
    var currentPosition : String = ""

    // set the playersArray by position
    var posArray = ceoArray


    // Button to dismiss ViewControllerB
    @IBAction func closeButton(_ sender: UIButton) {
        dismiss(animated: true, completion: nil)
    }


    // Picker view
    @IBOutlet weak var posPickerView: UIPickerView!


    override func viewDidLoad() {
        super.viewDidLoad()

        // select appropriate array based on position selected
        selectArray(currentPos: currentPosition)

        // Delegate picker view to self
        posPickerView.delegate = self
        posPickerView.dataSource = self

    }


    // UIPickerViewMethods
    // Set the number of picker columns to 1
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }

    // Set the number of picker rows to the number of items in posArray
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return posArray
    }

    // Set the title of each picker row to each name in posArray
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return posArray[row].name
    }


    // Picker action
    // What happens when selection is made
    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {

        print(posArray[row])

        // I've removed what's in here as it's not relevant to the question

    }


    // Method to select correct array based on currentPosition -- called in viewDidLoad
    func selectArray(currentPos: String) {

        switch (currentPos) {
        case "CEO" :
            posArray = ceoArray
        case "CFO" :
            posArray = cfoArray
        default :
            posArray = ceoArray
        }

    }


}

我需要在从ViewControllerA到ViewControllerB的第一个序列中将UIPickerView更新为相关的数组，而不是在第一个序列中使用默认值。

Answer 1

如果多个控件导致相同的segue，则需要在prepare(for:)函数中检查sender 。 如果是CEO按钮，则设置CEO字符串等：

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    guard segue.identifier == "SegueAtoB",
          let vc = segue.destination as? ViewControllerB,
          let senderButton = sender as? UIButton   else { return }

    vc.ReceivePlayerDataDelegate = self
    if (senderButton === selectButton_CEO) {
        vc.currentPosition = "CEO"
    } else if (senderButton === selectButton_CFO) {
        vc.currentPosition = "CFO"
    } // and so on
}