ios - 创建数组时发生 fatal error

Question

这是我的代码。基本上，当用户首先选择餐饮质量时，是精致(20%)、休闲(15%)还是酒吧(11%)。然后，用户将被询问有关食品质量、服务等的 1-5 分等级。具体取决于他们选择的数字，例如，如果高级餐厅是 5/5，那么它将在已经 20 的基础上增加 4%百分比(每个数字都会有一个选定的值添加到小费中)。谁能弄清楚发生了什么事吗？或者是否有更好的方法。

import UIKit

@IBDesignable

class ViewController: UIViewController {



    @IBOutlet weak var billTotal: UITextField!

    var diningValue: Double = 0.0
    @IBAction func toggleFineDining(sender: UIButton) {
        sender.highlighted = sender.selected
        if sender.selected == true{
            diningValue = 0.20
        }
    }
    @IBAction func toggleCasualDining(sender: UIButton) {
        sender.highlighted = sender.selected
        if sender.selected == true{
            diningValue = 0.15
        }
    }
    @IBAction func toggleBartender(sender: UIButton) {
        sender.highlighted = sender.selected
        if sender.selected == true{
            diningValue = 0.11
        }
    }


    @IBOutlet weak var service: UITextField!
    @IBOutlet weak var friendliness: UITextField!
    @IBOutlet weak var foodQuality: UITextField!
    @IBOutlet weak var atmosphere: UITextField!
    @IBOutlet weak var overall: UITextField!
    @IBOutlet weak var recommend: UISwitch!
    @IBOutlet weak var total: UILabel!



    func totalBill(inputArray: [Double], value: Double, recommend: Bool)->Double{

        var array: [Double] = []

        let total = inputArray[0]

        for var i = 1; i < inputArray.count; ++i {

            array.append(inputArray[i] * 0.01)

        }

        let sum = array.reduce(0, combine: +)

        var totalTip = Double()

        if recommend == true{

            totalTip = sum + value

        } else {
            if sum < 0.15 {
                totalTip = 0.15
            } else {
                totalTip = sum + value
            }
        }

        let tipValue = totalTip * total

        return total + tipValue

    }



    @IBAction func calcTotal(sender: AnyObject) {
        var valueList = [String(service.text), String(friendliness.text), String(foodQuality.text), String(atmosphere.text), String(overall.text)]

        let list = doubleArray(valueList)



        print(list)

        let initialTotal = Double(billTotal.text!)

        let total_bill = totalBill(list, value: diningValue, recommend: recommend.selected)

        print("Total: ", total_bill)

        print(String(format: "%.3f", Double(total_bill)))

        total.text = "$" + String(format: "%.2f", Double(total_bill))

        //diningValue = diningValue




    }




    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.
    }


}

func doubleArray(list: [String])->[Double]{

    var doubledList: [Double] = []

    for element in 0...list.count{

        let doubledElement = Double(list[element])

        doubledList.append(doubledElement!)

    }

    return doubledList

}

Answer 1

您的问题出在最后一个函数中:

func doubleArray(list: [String])->[Double]{

    var doubledList: [Double] = []

    for element in 0...list.count{

        let doubledElement = Double(list[element])

        doubledList.append(doubledElement!)

    }

    return doubledList

}

您的循环从 0 开始循环至list.count它崩溃于 list[element]当element是 list.count (Out of Index)

您需要从 0...list.count 更改至0..<list.count :

func doubleArray(list: [String])->[Double]{

    var doubledList: [Double] = []

    for element in 0..<list.count{

        let doubledElement = Double(list[element])

        doubledList.append(doubledElement!)

    }

    return doubledList

}

我建议您以快速的方式做到这一点:

func doubleArray(list: [String])->[Double]{

    var doubledList: [Double] = []

    for element in list {
        doubledList.append(Double(element) ?? 0.0)
    }

    return doubledList

}

使用 map 的较短版本功能:

func doubleArray(list: [String])->[Double]{
    return list.map( { Double($0) ?? 0.0 })
}