数组中的数据未显示在第二个 UIPickerView 中

Question

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。基于数组的选择，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 中的选定选项来填充第二个 pickerview 的子主题列表。控制台显示所有数据都正确地通过了这个过程，但是数据没有填充到第二个 pickerview 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]
   }
}

Answer 1

如您所说，您在第二个屏幕上使用了单独的 viewController 对象。加载后，它将有一个空的 SubjectHandler 数组。

您应该在 viewController 秒之间传递数组。参见 this tutorial

数组中的数据未显示在第二个 UIPickerView 中

Data in array not showing up in second UIPickerView

xcode

uipickerview

ios

swift3