arrays - 收到错误 : “Cannot subscript a value of type ‘[Double]’ with an index of type ‘(Any) -> Int’ ”

Question

我收到错误:

“Cannot subscript a value of type ‘[Double]’ with an index of type ‘(Any) -> Int’” on the following line of code:

tipPer = tipPercentages[index]

这是我的其余代码(包括错误行):((对于糟糕的格式/语法感到抱歉，我是 Swift 的新手!))

import UIKit

class ViewController: UIViewController {

    var tipPer: Int = 0

    let defaults = UserDefaults.standard

    @IBOutlet weak var tipLabel: UILabel!
    @IBOutlet weak var totalLabel: UILabel!
    @IBOutlet weak var perPersonLabel: UILabel!
    @IBOutlet weak var billField: UITextField!
    @IBOutlet weak var peopleField: UITextField!
    @IBOutlet weak var tipControl: UISegmentedControl!


    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        // This is a good place to retrieve the default tip percentage from UserDefaults
        // and use it to update the tip amount
    }

    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.
    }

    @IBAction func onTap(_ sender: AnyObject) {

        view.endEditing(true)
    }


    @IBAction func calculateTip(_ sender: AnyObject) {

        let tipPercentages = [0.10, 0.15, 0.20]

        defaults.synchronize()



        if (tipControl.selectedSegmentIndex == 0) {
            let index = tipControl.selectedSegmentIndex
        }

        if (tipControl.selectedSegmentIndex == 1) {
            let index = tipControl.selectedSegmentIndex
        }

        if (tipControl.selectedSegmentIndex == 2) {
            let index = tipControl.selectedSegmentIndex
        }

        if (tipControl.selectedSegmentIndex == 3) {

            let index = defaults.integer(forKey: "defaultTipControlKey")
        }


        let tipPer = tipPercentages[index]
        let bill = Double(billField.text!) ?? 0
        let people = Double(peopleField.text!) ?? 1

        let tip = bill * tipPer
        let total = bill + tip
        let perPerson = total / people

        tipLabel.text = String(format: "$%.2f", tip)
        totalLabel.text = String(format: "$%.2f", total)
        perPersonLabel.text = String(format: "$%.2f Each", perPerson)

    }
}

我知道它必须通过将索引变量设置为整数来做一些事情，我试图这样做，但我遗漏了一些东西。任何帮助将不胜感激。

Answer 1

问题是您在所有 if block 中声明的 index 常量，因此它的范围对应于该 if block 所以它在 if block 之后对您不可用。要解决这个问题，请在 for if block 之前声明索引变量，而不是创建多个 if block ，您只需要像这样的单个 if condition。

var index = defaults.integer(forKey: "defaultTipControlKey") //Default value
if (tipControl.selectedSegmentIndex != 3) {
    index = tipControl.selectedSegmentIndex
}
let tipPer = tipPercentages[index]

注意:您的if 条件 没有任何意义，您只想在一个if block 之上获取索引。