将 NSObject 用于 UIViewDelegate 而不是 UIViewController答案

【问题标题】：Using NSObject for a UIViewDelegate instead of a UIViewController将 NSObject 用于 UIViewDelegate 而不是 UIViewController
【发布时间】：2014-12-01 00:09:28
【问题描述】：

我想将以下类用作我的 UIPickerViewDelegate

class TimePickerViewDelegate: NSObject, UIPickerViewDataSource, UIPickerViewDelegate  {

    let pickerData = ["Mozzarella","Gorgonzola","Provolone","Brie","Maytag Blue","Sharp Cheddar","Monterrey Jack","Stilton","Gouda","Goat Cheese", "Asiago"]

    //MARK: - Delegates and data sources
    //MARK: Data Sources
    func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {
        return 1
    }
    func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return pickerData.count
    }

    //MARK: Delegates
    func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String! {
        return pickerData[row]
    }

    func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        println( pickerData[row] )
    }
}

我正在我的主 UIViewController 中使用以下内容对其进行初始化

 override func viewDidLoad() {
    super.viewDidLoad()

    let timePickerViewDelegate = TimePickerViewDelegate()

    timePickerView.dataSource = timePickerViewDelegate
    timePickerView.delegate = timePickerViewDelegate
}

但是，当我执行应用程序时，出现以下错误。

2014-11-30 15:49:22.046 HausClock[78601:10273448] -[NSISEngine numberOfComponentsInPickerView:]: unrecognized selector sent to instance 0x7da406e0
2014-11-30 15:49:22.052 HausClock[78601:10273448] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSISEngine numberOfComponentsInPickerView:]: unrecognized selector sent to instance 0x7da406e0'

似乎告诉我我的 TimePicker 视图无法响应适当的选择器，但如果我将委托从 NSObject 移动到 UIViewController 并复制/粘贴委托函数，它可以正常工作。

【问题讨论】：

标签： swift uiviewcontroller uipickerview uipickerviewdelegate

【解决方案1】：

dataSource 和 delegate 是弱属性，您应该将 timePickerViewDelegate 声明为实例属性以持有对委托的强引用。

let timePickerViewDelegate = TimePickerViewDelegate()

override func viewDidLoad() {
    super.viewDidLoad()

    timePickerView.dataSource = timePickerViewDelegate
    timePickerView.delegate = timePickerViewDelegate
}

【讨论】：

完美运行。谢谢！永远不会从错误中猜到这一点。