swift - 如何将变量从 SecondViewController 传递到 TableViewController 中的 loadData() 函数？

Question

这是我的第一个 Swift/Firestore 练习应用程序，我正在尝试访问“AddEventViewController”文件中要在“EventTableViewController”文件中使用的变量(eventLocation、eventDate)。

但是我似乎无法弄清楚缺少什么或者我做错了。

非常感谢那些更有经验的人的帮助。非常感谢!

This is my Storyboard setup

EventTableViewController.swift

import UIKit
import FirebaseFirestore

class EventsTableViewController: UITableViewController {

 var eventsArray = [Event]()

 override func viewDidLoad() {
    super.viewDidLoad()
    loadData()
}

func loadData() {
// How to pass variables from 'AddEventViewController' and use it inside this function??

   Firestore.firestore().collection("Locations").document(??).collection("Dates").document(??).collection("Events").getDocuments() { (querySnapshot, error) in
        if let error = error {
            print("Error getting documents: \(error)")
        } else {
            self.eventsArray = querySnapshot!.documents.compactMap({Event(dictionary: $0.data())})
            DispatchQueue.main.async {
                self.tableView.reloadData()
            }
        }
    }
}
override func numberOfSections(in tableView: UITableView) -> Int {
    // #warning Incomplete implementation, return the number of sections
    return 1
}

override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    // #warning Incomplete implementation, return the number of rows
    return eventsArray.count
}


override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "eventCell", for: indexPath)

    let event = eventsArray[indexPath.row]

    // Configure the cell...
    cell.textLabel?.text = "\(event.programType)"
    cell.detailTextLabel?.text = "\(event.eventLocation) \(event.eventDate)"

    return cell
}

AddEventViewController.swift

import UIKit
import FirebaseFirestore

class AddEventViewController: UIViewController {

@IBOutlet weak var eventLocation: UITextField!
@IBOutlet weak var eventDate: UITextField!
@IBOutlet weak var programType: UITextField!

override func viewDidLoad() {
    super.viewDidLoad()
}

@IBAction func saveEventButtonTapped(_ sender: UIBarButtonItem) {
// Check if textfields are not empty
    guard let EventLocation = eventLocation.text, !EventLocation.isEmpty else { return }
    guard let EventDate = eventDate.text, !EventDate.isEmpty else { return }
    guard let Program = programType.text, !Program.isEmpty else {return}

**// need to find a way to pass variables i.e. eventLocation and eventDate to 'EventsTableViewController'**        

    // Save profile details of person to Firestore as data fields
    let eventDetail: [String: Any] = ["Event Location": EventLocation, "Event Date": EventDate, "Program": Program]

    // Write data to Firestore
    Firestore.firestore().collection("Locations").document(EventLocation).collection("Dates").document(EventDate).collection("Events").document(Program).setData(eventDetail)
    { error in
        if let error = error {
            print("ERROR: Event not saved to database. Please try again! \(error)")
        } else {
            print("Event has been saved to the database!")
        }
        self.dismiss(animated: true, completion: nil)
    }
}

Event.swift

struct Event {
var programType: String
var eventLocation: String
var eventDate: String

var dictionary: [String: Any] {
    return [
        "programType": programType,
        "eventLocation" : eventLocation,
        "eventDate" : eventDate
    ]
}
}

extension Event : DocumentSerializable {
init?(dictionary: [String: Any]) {
    guard let programType = dictionary["Program"] as? String,
        let eventLocation = dictionary["Event Location"] as? String,
        let eventDate = dictionary["Event Date"] as? String else { return nil}

    self.init(programType: programType, eventLocation: eventLocation, eventDate: eventDate)
}
}

Answer 1

有一种方法可以做到这一点，您可以将 loadData() 添加到 viewWillAppear 方法中，如下所示:

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    loadData()
}

并将其从viewDidLoad中删除，因为viewDidLoad在 View 加载时只会调用一次。但是 viewWillAppear 每次访问 View 时都会调用。因此，每次您返回到上一个 View 时，它都会从服务器获取新数据。