如何在 ViewController 之外符合 UIPickerViewDelegate 和 UIPickerViewDataSource？

Question

我想在一个场景中拥有多个 UIPickerView，而不会使我的视图控制器因委托函数而膨胀。我在 UIPickerViews 上看到的所有教程都建议使用视图控制器本身作为 UIPickerView.

的委托

如何将此委托代码移出 ViewController？

受到 this tutorial 的启发，这里是一个视图控制器，它将自己指定为它的 UIPickerViews 的委托。我批评用于将行为映射到每个 UIPickerView:

的 if/else 逻辑

import UIKit

class ViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {

    @IBOutlet weak var pickerViewA: UIPickerView!
    @IBOutlet weak var pickerViewB: UIPickerView!

    let contentsA = ["1A", "2A", "3A"]
    let contentsB = ["1B", "2B", "3B", "4B"]

    override func viewDidLoad() {
        super.viewDidLoad()
        pickerViewA.delegate   = self
        pickerViewA.dataSource = self
        pickerViewB.delegate   = self
        pickerViewB.dataSource = self
    }

    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1 //Applies to both pickerViewA & pickerViewB
    }

    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        if pickerView == pickerViewA {
            return contentsA.count
        } else {
            return contentsB.count
        }
    }

    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        if pickerView == pickerViewA {
            return contentsA[row]
        } else {
            return contentsB[row]
        }
    }

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        if pickerView == pickerViewA {
            // Do something A
        } else {
            // Do something B
        }
    }
}

理想情况下，我希望有一个符合这些协议的自定义 class，然后为每个 UIPickerView 创建此 class 的新实例，以便它们具有唯一性委托和行为。

当我尝试定义一个名为 'PickerDelegate' 的单独 class 并符合 UIPickerViewDelegate 和 UIPickerViewDataSource 时，我在 Xcode 中收到此错误：

Type 'PickerDelegate' does not conform to protocol 'NSObjectProtocol'

显然 UIPickerViewDelegate & UIPickerViewDataSource 继承自 NSObjectProtocol。如果我添加协议存根（如 Xcode 所建议的），我会得到一长串我不热衷于实现的功能。

是否有更简单的方法在视图控制器之外遵守这些协议？

Answer 1

When I attempt to define a separate class called 'PickerDelegate' that conforms to UIPickerViewDelegate & UIPickerViewDataSource, I get this error in Xcode:

只需让您的 PickerDelegate 成为 NSObject 的子类即可。

class PickerDelegate : NSObject, UIPickerViewDelegate, UIPickerViewDataSource {

这不是强加，而是必要的，因为 Cocoa 是 Objective-C，否则甚至无法看到您的委托和数据源方法。

Answer 2

你可以像这样添加扩展，在任何你想使用 UIpiker 的 UIviewController 中，只需在视图 didload() 中设置委托

extension UIViewController: UIPickerViewDelegate, UIPickerViewDataSource {
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        if pickerView == pickerViewA {
            return contentsA.count
        } else {
            return contentsB.count
        }
    }

    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        if pickerView == pickerViewA {
            return contentsA[row]
        } else {
            return contentsB[row]
        }
    }

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        if pickerView == pickerViewA {
            // Do something A
        } else {
            // Do something B
        }
    }
}

如何在 ViewController 之外符合 UIPickerViewDelegate 和 UIPickerViewDataSource？

How conform to UIPickerViewDelegate and UIPickerViewDataSource outside of a ViewController?

uipickerview

ios

uipickerviewdatasource

uipickerviewdelegate

swift