ios - 在 Swift 中，如何使用传递给函数的 String 参数来引用 UILabel 变量？

Question

在 Swift 中，有没有一种方法可以通过引用传递给函数的字符串参数来分配变量？

我的目标是编写一个通用函数，允许我根据 UILabel 的字符串参数更新其文本。具体来说，该函数应通过将其变量名与其接收到的字符串参数进行匹配来找到 UILabel。

当我在分配变量值时尝试连接两个字符串时，出现以下错误:“String”不可转换为“Int”且“String”不可转换为“UILabel”。

也许我做错了。

import UIKit

class ViewController: UIViewController {

    // Setup variables
    var appleCounter = 0, appleFarms = 1
    var orangeCounter = 0, orangeFarms = 1
    var grapeCounter = 0, grapeFarms = 1

    // Setup labels
    @IBOutlet weak var appleLabel: UILabel!
    @IBOutlet weak var orangeLabel: UILabel!
    @IBOutlet weak var grapeLabel: UILabel!

    // Function to update label
    func updateFruitLabel(fruitString: String) {

        let fruitCount: Int = (fruitString + "Counter") // error: 'String' is not convertible to 'Int'
        let fruitFarms: Int = (fruitString + "Farms") // error: 'String' is not convertible to 'Int'
        let fruitLabel: UILabel = (fruitString + "Label") // error: 'String' is not convertible to 'UILabel'

        fruitLabel.text = "\(fruitString)s: \(fruitCount), \(fruitString) farms: \(fruitFarms)"
    }

    // Setup buttons
    // Increment fruit count and call update label function
    @IBAction func appleTapped(sender: UIButton) {
        appleCounter++
        updateFruitLabel("apple")
    }

    @IBAction func orangeTapped(sender: UIButton) {
        orangeCounter++
        updateFruitLabel("orange")
    }

    @IBAction func grapeTapped(sender: UIButton) {
        grapeCounter++
        updateFruitLabel("grape")
    }


    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

Answer 1

看看枚举和开关。下面是一些适合您的代码:

class ViewController: UIViewController {

    enum fruit {
        case apple
        case orange
        case grape
    }

    // Setup variables
    var appleCounter = 0, appleFarms = 1
    var orangeCounter = 0, orangeFarms = 1
    var grapeCounter = 0, grapeFarms = 1

    // Setup labels
    @IBOutlet weak var appleLabel: UILabel!
    @IBOutlet weak var orangeLabel: UILabel!
    @IBOutlet weak var grapeLabel: UILabel!

    // Function to update label
    func updateFruit(fruitSelected: fruit) {

        switch fruitSelected {
            case .apple: appleLabel.text = "\(++appleCounter)"
            case .orange: orangeLabel.text = "\(++orangeCounter)"
            case .grape: grapeLabel.text = "\(++grapeCounter)"
        }
    }

    // Setup buttons
    // Increment fruit count and call update label function
    @IBAction func appleTapped(sender: UIButton) {
        updateFruit(fruit.apple)
    }

    @IBAction func orangeTapped(sender: UIButton) {
        updateFruit(fruit.orange)
    }

    @IBAction func grapeTapped(sender: UIButton) {
       updateFruit(fruit.grape)
    }
}

或者更简单:

class ViewController: UIViewController {

    // Setup variables
    var appleCounter = 0, appleFarms = 1
    var orangeCounter = 0, orangeFarms = 1
    var grapeCounter = 0, grapeFarms = 1

    // Setup labels
    @IBOutlet weak var appleLabel: UILabel!
    @IBOutlet weak var orangeLabel: UILabel!
    @IBOutlet weak var grapeLabel: UILabel!

    // Setup buttons
    // Increment fruit count and call update label function
    @IBAction func appleTapped(sender: UIButton) {
        appleLabel.text = "\(++appleCounter)"
    }

    @IBAction func orangeTapped(sender: UIButton) {
        orangeLabel.text = "\(++orangeCounter)"
    }

    @IBAction func grapeTapped(sender: UIButton) {
       grapeLabel.text = "\(++grapeCounter)"
    }
}