Swift Generic UIPickerView

Picker.swift

class PickerSource : NSObject, UIPickerViewDelegate, UIPickerViewDataSource {
    
    var data: [[String]] = []
    var selectionUpdated: ((component: Int, row: Int) -> Void)?
    
    // MARK: UIPickerViewDataSource
    
    func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {
        return data.count
    }
    
    func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        let rows = data[component]
        return rows.count
    }
    
    // MARK: UIPickerViewDelegate
    
    func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String! {
        return "\(data[component][row])"
    }
    
    func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        selectionUpdated?(component: component, row: row)
    }
}

class Picker<T : Printable> : UIPickerView {
    
    var data: [[T]] = [] {
        didSet {
            source.data = data.map { $0.map { "\($0)" } }
            reloadAllComponents()
        }
    }
    
    var selectionUpdated: ((selections: [T?]) -> Void)?
    
    private let source = PickerSource()
    
    // MARK: Initialization
    
    convenience init() {
        self.init(frame: CGRectZero)
    }
    
    convenience init(data: [[T]]) {
        self.init(frame: CGRectZero)
        self.data = data
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }
    
    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setup()
    }
    
    // MARK: Setup
    
    private func setup() {
        dataSource = source
        delegate = source
        source.selectionUpdated = { [weak self] component, row in
            if let _self = self {
                var selections: [T?] = []
                for (idx, componentData) in enumerate(_self.data) {
                    let selectedRow = _self.selectedRowInComponent(idx)
                    if selectedRow >= 0 {
                        selections.append(componentData[selectedRow])
                    } else {
                        selections.append(nil)
                    }
                }
                _self.selectionUpdated?(selections: selections)
            }
        }
    }
}