使用.plist文件重新填充uipickerview

Question

我有4个.plist文件，我想用它来通过滑块填充UIPickerView，现在我可以在ViewDidLoad方法中填充第一个文件，即＆＃34; WeightUnits＆＃34;之一。

现在滑块在加载视图时从1开始具有1到4的值，但是当我向右滑动（值2）时，它应该使用下一个.plist文件重新填充UIPickerView但是由于某种原因它会崩溃，我想我知道原因所在，但我无法找到解决方案。 （我在代码中添加了评论）

请注意： UIPickerView连接到控制器委托和数据源

提前感谢任何帮助/解决方案

导入UIKit

类ConverterScript：UIViewController，UIPickerViewDelegate，UIPickerViewDataSource {

fileprivate let convertFromComponent = 0
fileprivate let convertToComponent = 1
fileprivate var convertFromTo:[String : [String]]!
fileprivate var convertFrom:[String]!
fileprivate var convertTo:[String]!
@IBOutlet weak var sliderLabel: UILabel!
@IBOutlet weak var converterPicker: UIPickerView!
@IBOutlet weak var slider: UISlider!
@IBOutlet weak var valueField: UILabel!
@IBOutlet weak var resultUnitOfMeasure: UILabel!

override func viewDidLoad() {
    super.viewDidLoad()

    sliderLabel.text = "Weight"

    let bundle = Bundle.main
    let plistURL = bundle.url(forResource: "WeightUnits", withExtension: ".plist")
    convertFromTo = NSDictionary(contentsOf: plistURL!) as! [String: [String]]
    let allWeights = convertFromTo.keys
    convertFrom = allWeights.sorted()

    let selectedWeight = convertFrom[0]
    convertTo = convertFromTo[selectedWeight]
    converterPicker.reloadComponent(convertFromComponent)
    converterPicker.reloadComponent(convertToComponent)
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

@IBAction func ifSliderChanges(_ sender: UISlider) {

    sliderLabel.text = "\(lroundf(sender.value))"

    if (sender.value < 1.5) {
        sliderLabel.text = "Weight"

        let bundle = Bundle.main
        let plistURL = bundle.url(forResource: "WeightUnits", withExtension: ".plist")
        convertFromTo = NSDictionary(contentsOf: plistURL!) as! [String: [String]]
        let allWeights = convertFromTo.keys
        convertFrom = allWeights.sorted()

        let selectedWeight = convertFrom[0]
        convertTo = convertFromTo[selectedWeight]
        converterPicker.reloadComponent(convertFromComponent)
        converterPicker.reloadComponent(convertToComponent)

        converterPicker.selectRow(0, inComponent: convertFromComponent, animated: true)
        converterPicker.selectRow(0, inComponent: convertToComponent, animated: true)
    } else if (sender.value >= 1.5 && sender.value <= 2.5){
        sliderLabel.text = "Volume"

        let bundle = Bundle.main
        let plistURL = bundle.url(forResource: "VolumeUnits", withExtension: ".plist")
        //issue starts here according to Xcode Debugging!!!!!
        convertFromTo = NSDictionary(contentsOf: plistURL!) as! [String: [String]]
        let allWeights = convertFromTo.keys
        convertFrom = allWeights.sorted()

        let selectedWeight = convertFrom[0]
        convertTo = convertFromTo[selectedWeight]
        converterPicker.reloadComponent(convertFromComponent)
        converterPicker.reloadComponent(convertToComponent)

        converterPicker.selectRow(0, inComponent: convertFromComponent, animated: true)
        converterPicker.selectRow(0, inComponent: convertToComponent, animated: true)
    }else if (sender.value >= 2.5 && sender.value <= 3.5){
        sliderLabel.text = "Length"

        let bundle = Bundle.main
        let plistURL = bundle.url(forResource: "LengthUnits", withExtension: ".plist")
        convertFromTo = NSDictionary(contentsOf: plistURL!) as! [String: [String]]
        let allWeights = convertFromTo.keys
        convertFrom = allWeights.sorted()

        let selectedWeight = convertFrom[0]
        convertTo = convertFromTo[selectedWeight]
        converterPicker.reloadComponent(convertFromComponent)
        converterPicker.reloadComponent(convertToComponent)

        converterPicker.selectRow(0, inComponent: convertFromComponent, animated: true)
        converterPicker.selectRow(0, inComponent: convertToComponent, animated: true)
    }
    else if (sender.value > 3.5){
        sliderLabel.text = "Temperature"

        let bundle = Bundle.main
        let plistURL = bundle.url(forResource: "TemperatureUnits", withExtension: ".plist")
        convertFromTo = NSDictionary(contentsOf: plistURL!) as! [String: [String]]
        let allWeights = convertFromTo.keys
        convertFrom = allWeights.sorted()

        let selectedWeight = convertFrom[0]
        convertTo = convertFromTo[selectedWeight]
        converterPicker.reloadComponent(convertFromComponent)
        converterPicker.reloadComponent(convertToComponent)

        converterPicker.selectRow(0, inComponent: convertFromComponent, animated: true)
        converterPicker.selectRow(0, inComponent: convertToComponent, animated: true)
    }

}

@IBAction func onButtonPressed(_ sender: UIButton) {

    let convertFromRow = converterPicker.selectedRow(inComponent: convertFromComponent)
    let convertToRow = converterPicker.selectedRow(inComponent: convertToComponent)

    let from = convertFrom[convertFromRow]
    let to = convertTo[convertToRow]

    if valueField.text?.isEmpty ?? true {
        let title = "error"
        let message = "please enter a value"

        let alert = UIAlertController(
            title: title,
            message: message,
            preferredStyle: .alert)
        let action = UIAlertAction(
            title: "OK",
            style: .default,
            handler: nil)
        alert.addAction(action)
        present(alert, animated: true, completion: nil)
    } else{
        if (slider.value < 1.5) {

        } else if (slider.value >= 1.5 && slider.value <= 2.5){

        }else if (slider.value >= 2.5 && slider.value <= 3.5){

        }
        else if (slider.value > 3.5){

        }
    }

    resultUnitOfMeasure.text = "\(to)"
}


func numberOfComponents(in pickerView: UIPickerView) -> Int {
    return 2
}

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    if component == convertFromComponent {
        return convertFrom.count
    } else {
        return convertTo.count
    }
}

//Picker View Delegate Method
func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
    if component == convertFromComponent {
        return convertFrom[row]
    } else {
        return convertTo[row]
    }
}

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    if component == convertFromComponent {
        let selectedWeight = convertFrom[row]
        convertTo = convertFromTo[selectedWeight]
        converterPicker.reloadComponent(convertToComponent)
    }
}

}