数组中的数据未显示在第二个 UIPickerView 中

Posted 2023-02-24

【中文标题】数组中的数据未显示在第二个 UIPickerView 中

【英文标题】：Data in array not showing up in second UIPickerView

【发布时间】：2017-07-27 16:18:16

【问题描述】：

我是 ios 开发的新手，所以请记住我的问题。我正在开发一个将显示初始数组的应用程序。根据数组的选择，第二个pickerview（显示在下一个视图控制器中）将使用字典和第一个pickerview中的选定选项来使用子主题列表填充第二个pickerview。控制台显示所有数据都正确地通过了该过程，但是数据没有填充到第二个选择器视图中。有人可以看看我的代码并告诉我哪里出错了吗？

import UIKit
import Foundation

class ViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource 

   @IBOutlet weak var pickerView: UIPickerView!

   @IBAction func SubjectSelected(_ sender: UIButton, forEvent event: UIEvent) 
      SubjectHandler = subSubjects[SelectedSubject]!
      print(SubjectHandler)
      print(Subjects)
   

   //Create instances of the selected subject & the subject handler (in case SelectedSubject is not empty)
   var SelectedSubject: String = ""
   var SubjectHandler: Array<String> = []

   //Define primary values for both subjects and subSubjects//
   let Subjects: Array = ["Macroeconomics", "Microeconomics", "Financial Economics", "Game Theory",  "Econometrics", "Law Economics", "Public Sector Economics", "International Economics", "General Statistics"]

   let subSubjects = [
      "Macroeconomics":
         ["GDP", "Accounting Methods", "Labor Market", "DMP Job Search Model", "Keynesian Economics", "Sticky-Price Model", "Elasitcity", "Supply and Demand"],

      "Microeconomics":
         ["Elasticity", "Consumer Theory", "Preference Curves", "Competitive Models", "Scarcity"],

      "Financial Economics":
         ["Interest", "Dividends Returns", "Return & Expected Return"],

      "Game Theory":
         ["Nash Equilibrium", "Dominant Strategies", "Iterated Games", "Backwards Induction", "Extensive Form Games"],

      "Econometrics":
         ["Capital Asset Pricing Model", "Regressional Analysis", "Modeling Rules", "Central Limit Theorem", "Probablitiy & Distribution","Heteroscedasticity", "Weighted Least Squares", "Sampling Distributions"],

      "Law Economics":
         ["Externalities", "Damages Calculations", "Property Rights Ownership", "Claims", "Ownership Principles"],

      "Public Sector Economics": ["Valuations", "Tax Income Calculations", "Budget Analysis"], "International Economics": ["Taxing Methods", "Importing and Exporting", "Currency Exchange Rates", "Tarrifs", "GDP", "Product Purchase Parity"],

      "General Statistics":
         ["Z-Scores", "Summary Statistics", "One-Tailed Hypothesis Testing", "Two-Tailed Hypothesis Testing", "Confidence Intervals", "Upper and Lower Bounds"]
   ]

   override func viewDidLoad() 
      super.viewDidLoad()
      // Do any additional setup after loading the view, typically from a nib.

      pickerView.delegate = self
      pickerView.dataSource = self
      if pickerView.tag == 2 
         pickerView.reloadAllComponents()
      
   

   override func didReceiveMemoryWarning() 
      super.didReceiveMemoryWarning()
      // Dispose of any resources that can be recreated.
   

   func numberOfComponents(in pickerView: UIPickerView) -> Int 
      return 1
   
   func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int 
      if pickerView.tag == 1 
         return Subjects.count
      
      else 
         return SubjectHandler.count
      
   
   func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? 
      if pickerView.tag == 1 
         return Subjects[row]
      
      else 
         return SubjectHandler[row]
      
   
   func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int)  
      SelectedSubject = Subjects[row]
   

【参考方案1】：

正如您所说，您在第二个屏幕上使用了一个单独的 viewController 对象。当它被加载时，它将有一个空的SubjectHandler 数组。

你应该在 viewController 之间传递数组。见this tutorial

【讨论】：

谢谢，我没有意识到每个屏幕都需要单独的视图控制器！

只是想跟进并让您知道您的回答帮助我解决了这个问题....几天来我一直在努力解决这个问题！再次感谢您

很高兴为您提供帮助。祝你的应用好运！