ios - Pickerview 委托(delegate) UIView : array index out of range

Question

我创建了一个包含 2 个具有不同数据源的组件的选择器 View :

func pickerView(pickerView: UIPickerView, viewForRow row: Int, forComponent component: Int, reusingView view: UIView?) -> UIView {
    let pickerLabel = UILabel()
    let titleLabel = firstFieldArray[row]
    let titlelabel2 = secondFieldArray[row]

    if component == 0 {
    let myTitle = NSAttributedString(string: titleLabel, attributes: [NSFontAttributeName:UIFont(name: "Georgia", size: 15.0)!,NSForegroundColorAttributeName:UIColor.blackColor()])
    pickerLabel.attributedText = myTitle
    } else {
        let myTitle = NSAttributedString(string: titlelabel2, attributes: [NSFontAttributeName:UIFont(name: "Georgia", size: 15.0)!,NSForegroundColorAttributeName:UIColor.blackColor()])
        pickerLabel.attributedText = myTitle
    }
    return pickerLabel
}

这是我的数据模型:

class professionArrays {
    func professsionValues() -> [String] {

        return ["Engineer", "Information Technology", "Teacher"]
    }

    func subProfessionValues(profession: String) -> [String] {
        if profession == "Engineer" {
            return ["Electrical Engineer","Sex Engineer","Civil Engineer","Software Engineer"]
        } else if profession == "Information Technology" {
            return ["IT Programmer","UI/UX Designer","Tester/Debugger"]
        } else {
            return ["English Teacher", "Math Teacher", "Physics Teacher"]
        }

    }
}

当我选择 Engineer、Information Technology 和 Teacher 时，Picker View 显示数组，它在第二个组件中显示它们的 subProfessional 值。

错误被触发，例如当我选择信息技术并在第一个组件中选择工程师时，当我滑动第二个组件值时发生错误:

error : fatal error: Array index out of range

编辑:didSelectRow 委托(delegate)中的代码

func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    if component == 0 {
        let professionAndSubProfession = professionArrays()
        let currentValue = firstFieldArray[row]
        secondFieldArray = professionAndSubProfession.subProfessionValues(currentValue)
        pickerView.reloadAllComponents()
        firstProfessionCurrentValue = firstFieldArray[row]
        print(firstProfessionCurrentValue)
        selectedProfessionLabel.text = firstProfessionCurrentValue
        professionTextfield.text = firstProfessionCurrentValue


    } else {

        secondSubProfessionCurrentValue = secondFieldArray[row]
        selectedSubProfessionLabel.text = secondSubProfessionCurrentValue
        professionTextfield.text = "\(firstProfessionCurrentValue!) - \(secondSubProfessionCurrentValue!)"
        print(secondSubProfessionCurrentValue)
        pickerView.reloadAllComponents()

    }

}

Answer 1

工程师的子职业在其数组中有 4 个值，从您与我们共享的代码中，我可以看出这是唯一可能导致该错误的问题。

如果 UIPickerView 试图在第二个组件中显示第 4 行，它将调用委托(delegate)(如您发布的那样)。在该实现中，您调用 firstFieldArray[row]。此时行为 3，但 firstFieldArray 只有 3 个值，因此此时它的最大索引为 2。

简而言之，如果组件为 1，则不要创建 titleLabel；否则，如果组件为 0，则不要创建 titleLabel2。如果您不确定数组是否包含您尝试获取的值的数量的索引，做一些防御性编码:

// Check if the array holds the same or more values then 'row'
if array.count > row {
    return array[row]
}

编辑

这是一个关于如何改进委托(delegate)实现的示例。 这样，您的代码就不会尝试从错误的数组中获取项目。每次从选取器中选择一个新项目时，您已经重新加载了 pickerView 组件，因此它应该再次调用 DataSource & Delegates。

// UIPickerViewDataSource
func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int
    if component == 0 {
        return firstFieldArray.count
    } else {
        return secondFieldArray.count
    }
}

//UIPickerViewDelegate
func pickerView(pickerView: UIPickerView, viewForRow row: Int, forComponent component: Int, reusingView view: UIView?) -> UIView {
    let pickerLabel = UILabel()

    if component == 0 {
        // By placing it within the if-statement, this array won't be searched by index unnecassary.
        // So even if the second component would hold 4 or more items, it won't try to fetch 4th or higher index from this first array.
        let titleLabel = firstFieldArray[row]
        let myTitle = NSAttributedString(string: titleLabel, attributes: [NSFontAttributeName:UIFont(name: "Georgia", size: 15.0)!,NSForegroundColorAttributeName:UIColor.blackColor()])
        pickerLabel.attributedText = myTitle
    } else {
        let titlelabel2 = secondFieldArray[row]
        let myTitle = NSAttributedString(string: titlelabel2, attributes: [NSFontAttributeName:UIFont(name: "Georgia", size: 15.0)!,NSForegroundColorAttributeName:UIColor.blackColor()])
        pickerLabel.attributedText = myTitle
    }
    return pickerLabel
}