如何将第二个UIPickerView关联至自定义代理以实现独立控制？

其实你当前的思路有点绕啦——UIPickerView只会主动调用UIPickerViewDelegate和UIPickerViewDataSource协议里的方法，你自定义的secondDelegate和secondDelegateDataSource并不会被系统自动触发，所以哪怕你写了这些方法，p2也不会去调用它们。

想要不用if判断分别控制两个Picker，更简洁的方式是给每个Picker创建独立的代理类，各自实现标准的UIPickerView代理协议，这样每个Picker绑定自己的代理，完全不用区分Picker实例。

下面是调整后的完整代码：

首先定义两个代理类，各自负责对应Picker的数据和交互：

import UIKit

// 第一个Picker的代理类
class Picker1Delegate: NSObject, UIPickerViewDelegate, UIPickerViewDataSource {
    private let data = ["1","3","5"]
    
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }
    
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return data.count
    }
    
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return data[row]
    }
}

// 第二个Picker的代理类
class Picker2Delegate: NSObject, UIPickerViewDelegate, UIPickerViewDataSource {
    private let data = ["2","4","6"]
    
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }
    
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return data.count
    }
    
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return data[row]
    }
}

然后在ViewController里实例化这两个代理，绑定到对应的Picker上：

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // 实例化两个代理
        let picker1Delegate = Picker1Delegate()
        let picker2Delegate = Picker2Delegate()
        
        // 绑定代理和数据源
        p1.delegate = picker1Delegate
        p1.dataSource = picker1Delegate
        p2.delegate = picker2Delegate
        p2.dataSource = picker2Delegate
        
        // 注意：要把代理对象存为ViewController的属性，否则会被ARC释放
        self.picker1Delegate = picker1Delegate
        self.picker2Delegate = picker2Delegate
    }
    
    @IBOutlet weak var p1: UIPickerView!
    @IBOutlet weak var p2: UIPickerView!
    
    // 存储代理对象，避免被自动释放
    private var picker1Delegate: Picker1Delegate?
    private var picker2Delegate: Picker2Delegate?
}

关键说明： #

• 每个代理类只负责自己的Picker逻辑，职责单一，代码更清晰
• 必须把代理对象存为ViewController的属性，否则创建后会被自动释放，Picker会失去代理
• 完全不需要用if pickerView == p1这类判断，每个Picker的逻辑完全隔离

内容的提问来源于stack exchange，提问作者bruno617