swift - 将 NSObject 用于 UIViewDelegate 而不是 UIViewController

Question

我有以下要用作 UIPickerViewDelegate 的类

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，但是如果我将委托从 NSObject 移动到 UIViewController 并复制/粘贴委托函数，它就可以正常工作。

Answer 1

dataSource并且delegate是弱属性，您应该声明timePickerViewDelegate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
}