使用segue将数据从ViewController传递到TableViewController

Question

我在Xcode中使用Swift创建了一个计算器。我想为它添加另一个功能，我已经有一个显示以前计算的历史标签。我想将该历史记录标签中显示的数据传递给TableViewController，并且对于每个计算，我的历史记录标签显示它将每个数据添加到我的TableViewController中。我知道我应该可以使用perform segue，但我不确定。到目前为止，这是我的代码：

ViewController.swift

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var displayLabel: UILabel!
    @IBOutlet weak var HistoryLabel: UILabel!

    var userIsTypingNumbers = false

    @IBAction private func NumbersEntered(_ sender: UIButton) {
        //know what number is being pressed
        let digit = sender.currentTitle!
        //if user is typing a number, do this.
        if userIsTypingNumbers{
            //specify what number is being pressed
            let textCurrentDisplay = displayLabel.text!
            //append the another number onto the previous number.
            displayLabel.text = textCurrentDisplay + digit
        } else {
            displayLabel.text = digit
        }
        userIsTypingNumbers = true
    }
    var displayValue: Double {

        get {
            return Double(displayLabel.text!)!
        }
        set {
            displayLabel.text = String(newValue)
        }
    }

    private var calculations = PerformCalculations()

    @IBAction func Enter(_ sender: UIButton) {
        //perform the calculations
        if userIsTypingNumbers{
            calculations.setOperand(operand: displayValue)
            userIsTypingNumbers = false
        }
        if let mathematicalSymbol = sender.currentTitle {
            calculations.performOperation(symbol: mathematicalSymbol)
        }
        HistoryLabel.text = HistoryLabel.text! + String(sender.currentTitle!);displayValue = calculations.result
        HistoryLabel.text = HistoryLabel.text! + String(displayValue)

    }


    @IBAction func Clear(_ sender: UIButton) {
        //clear display to 0.
        displayLabel.text = "0"
        HistoryLabel.text = ""
    }

    @IBAction func Delete(_ sender: UIButton) {
        //deleting last typed number, if user messed up.
        let name: String = self.displayLabel.text!
        //count number of characters.
        let stringLength = name.characters.count
        let substringIndex = stringLength - 1
        displayLabel.text = (name as NSString).substring(to: substringIndex)
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if (segue.identifier == "History"){
            if let destinationVC = segue.destination as? HistoryClassViewController{
                destinationVC
            }
        }

    }
}

我已经开始尝试准备segue功能，但不确定如何使其工作。任何帮助将非常感激。希望这是有道理的。这是我的计算器如何在Xcode中布局的图片：

Answer 1

在您的HistoryClassViewController字段中创建

var someData: Any!

然后：

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "History" {
        if let destinationVC = segue.destination as! HistoryClassViewController {
            destinationVC.someData = something
        }
    }
}

然后执行segue，你想输入：

self.performSegue(withIdentifier: "History", sender: self)

希望有所帮助

Answer 2

在 HistoryClassViewController类

中将字符串变量作为全局变量

示例：

class HistoryClassViewController: UITableViewController{
    var dataString:String!

    //............Continue code
    //............

现在在ViewController类中编写此方法

 override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
            if (segue.identifier == "History"){
                if let destinationVC = segue.destination as? HistoryClassViewController{
                    destinationVC.dataString = displayLabel.text!
                }
            }

    }

最后在TableViewController中访问dataString值。