Swift 中 UIPickerView 的自定义数据源类

Posted 2023-02-24

【中文标题】Swift 中 UIPickerView 的自定义数据源类

【英文标题】：Custom data source class for UIPickerView in Swift

【发布时间】：2016-03-27 16:26:37

【问题描述】：

我想像这样为 UIPickerView 创建一个单独的数据源类：

class PickerData : NSObject, UIPickerViewDataSource 
    // class definition goes here
    var pickerDataSource = ["White", "Red", "Green", "Blue"];


    func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int 
        return 1
    

    func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int 
        return pickerDataSource.count;
    

    func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String! 
        return pickerDataSource[row]
    

当我尝试使用它时，我得到Thread 1: EXC_BAD_ACCESS ( code=1, address=0x0)

func createPickerView() -> UIView 
    var picker = UIPickerView(frame:CGRectMake(20, 20, 480, 20))
    picker.dataSource = PickerData();
    picker.delegate = self;

    var newView = UIView();
    newView.setTranslatesAutoresizingMaskIntoConstraints(false);
    newView.backgroundColor = UIColor.whiteColor();

    newView.addSubview(picker)
    self.view.addSubview(newView) // <-- ERROR HERE
    return newView;

但是，如果我将 dataSource 更改为 self 它可以解决问题：

picker.dataSource = self; 
// and add the functions numberOfComponentsInPickerView etc to the
// main controller it works

但我不想使用self，因为这会将代码限制为一页上只有一个 UIPickerView。也许这还不错，但感觉有点悲伤的设计。

【问题讨论】：

啊哈，函数退出后数据源变量的引用计数归零，所以必须设置为视图控制器的成员变量之类的。

【参考方案1】：

是的。我认为特罗是对的。最好将数据源对象设置为视图控制器上的变量。见下文（撰写本文时为 Swift 3）：

import UIKit

class MyViewController: UIViewController, UIPickerViewDelegate 

    var pickerDataSource = PickerData()

    //...
    // other properties, viewDidLoad, etc.
    //...

    func createPickerView() -> UIView 
        var picker = UIPickerView(frame: CGRect(x: 20, y: 20, width: 480, height: 20))
        picker.dataSource = pickerDataSource // Data source now set to member of MyViewController
        picker.delegate = self

        var newView = UIView()
        newView.translatesAutoresizingMaskIntoConstraints = false
        newView.backgroundColor = UIColor.white

        newView.addSubview(picker)
        self.view.addSubview(newView)
        return newView
    



class PickerData: NSObject, UIPickerViewDataSource 

    // Data source properties, initializer and methods here...