Reset the value of the 1st component of UIPickerView when component 0 is changed

问题

I can't figure out how to reset to component 0 the array used in the first component of the PickerView, when component 0 is changed (in order to avoid possible errors due to indexOutOfRange).

This is the structure of my data

let bananas = ["banana1", "banana2"]
let fruitArray = ["banana1" : ["cherry1","cherry2"], "banana2" : ["cherry1", "cherry2", "cherry3"]]


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

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    if component == 0 {
        return bananas.count
    }
    else {
        let selectedBanana = pickerView.selectedRow(inComponent: 0)
        return fruitArray[banana[selectedBanana]]!.count
    }
}

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {


    let selectedBanana = pickerView.selectedRow(inComponent: 0)
    let selectedCherry = pickerView.selectedRow(inComponent: 1)


    bananaPicked = bananas[selectedBanana]
    cherryPicked = fruitArray[bananaPicked]![selectedCherry]


    pickerView.reloadAllComponents() 
    }


func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
if component == 0 {
    return bananas[row]
}
else {
    let selectedBanana = pickerView.selectedRow(inComponent: 0)
    return fruitArray[selectedBanana]![row]
}
}

Right now when I'm (let's say) in banana2 and cherry3, but I switch to banana1, I get an indexOutOfRange error, because of course the first banana array does not have a third item. My wish it whenever the banana row is changed to reset to 0 the cherry row.

__________ UPDATE ______________ This is another error cause the crashing that I found (indexOutOfRange), I posted a screenshot.

回答1:

Set the selected row to 0 in component 1 when component 0 is changed.

Also, there is no need to reload all of the components. Only component 1 needs reloading.

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {

    if component == 0 {
        pickerView.selectRow(0, inComponent: 1, animated: false)
    }

    let selectedBanana = pickerView.selectedRow(inComponent: 0)
    let selectedCherry = pickerView.selectedRow(inComponent: 1)

    bananaPicked = bananas[selectedBanana]
    cherryPicked = fruitArray[bananaPicked]![selectedCherry]

    //pickerView.reloadAllComponents()
    pickerView.reloadComponent(1)
}

For your second crash, try some defensive programming to avoid the crash:

func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
    if component == 0 {
        return bananas[row]
    }
    else {
        let selectedBanana = pickerView.selectedRow(inComponent: 0)
        let rowData = fruitArray[bananas[selectedBanana]]!
        if rowData.indices.contains(row) {
            return rowData[row]
        } else {
            return nil
        }
    }
}

来源：https://stackoverflow.com/questions/55893829/reset-the-value-of-the-1st-component-of-uipickerview-when-component-0-is-changed

标签

arrays

swift

uipickerview