收到錯誤：「不能與類型的索引，下標類型的‘[雙]’值‘（任何） - >內部’」

Question

我收到錯誤：

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

tipPer = tipPercentages[index] 

這裏是我的代碼的其餘部分（包括錯誤路線）：（（抱歉可怕的格式/語法，我是新來的斯威夫特）！）

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，它必須做一些事情將索引變量設置爲一個整數我試圖做，但我錯過了一些東西。任何幫助，將不勝感激。

Answer 1

的問題是，您已聲明裏面的所有if block所以它的範圍是對應於if block，因此它if block對你以後不可index不變。爲了解決這個問題，在if for塊之前聲明索引變量，而不是創建多個if塊，你只需要這樣一個單獨的if condition。

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

注：您if condition並不會讓你只是想一個單一if block上面得到的索引任何意義。