从Firebase数据库加载Swift Tableview数据

Question

I am currently trying to display data from my real-time database of Firebase in different tableviews.

In my first tableview I load my first level of my database structure (this already works).

Now I want to see what the user selects in the first tableview, and then display the next level of my database in a new TableView.

I have a function in my second TableViewController.swift file where to save in the selected row from the first TableView.

This way I want to save the next level from my database into an array so that this data will be displayed in my second tableview. When I then debug my new array, I also see the correct data in the new array. However, the data is not displayed in the second TableView.

I guess it's because the data is not 100% ready before the TableView loads.

Do you have a tip?

Firebase Structure:

-sports
    -Bicycle
        -BMX
            -Bike 1
                -img: „bike1.png“
                -text: „bike 1“
            -Bike 2
                -img: „bike2.png“
                -text: „bike 1“
    -Car
        -Audi
            -Car 1
                -img: „car1.png“
                -text: „car 1“
            -Car 2
                -img: „car2.png“
                -text: „car 2“

FirstTableViewController:

import UIKit
import Firebase

class FirstTableViewController: UITableViewController {

    var categorie = [String]()

    func loadData() {
        var ref: DatabaseReference!
        ref = Database.database().reference()

        ref.child("sports").observeSingleEvent(of: .value, with: { snapshot in
            if let sports = snapshot.value as? [String: Any] {
                for (title, _) in sports {
                    self.categorie.append(title)
                    self.tableView.reloadData()
                }
            }
        })
    }

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

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return categorie.count
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "sportCell")
        cell?.textLabel?.text = categorie[indexPath.row]
        return cell!
    }

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        // Set the segue's identifier in the Storyboard
        performSegue(withIdentifier: "firstToSecond", sender: self)
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "firstToSecond" {
            guard let destination = segue.destination as? SecondTableViewController,
                let indexPath = tableView.indexPathForSelectedRow else { return }
            destination.detailedValue = categorie[indexPath.row]
        }
    }
}

SecondTableViewController:

import UIKit
import Firebase

class SecondTableViewController: UITableViewController {

    var detailedValue: String?
    var secondArray = [String]()

    func setIndex(value: String) {
        loadData(index: value)
    }

    func loadData(index: String) {
        var ref: DatabaseReference!
        ref = Database.database().reference()

        if (index != "") {
            ref.child("sports").child(index).observeSingleEvent(of: .value, with: { snapshot in
                if let sports = snapshot.value as? [String: Any] {
                    for (title, _) in sports {
                        self.secondArray.append(title)
                        self.tableView.reloadData()
                    }
                }
            })
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        if let detailedValue = detailedValue {
            loadData(index: detailedValue)
        }
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return secondArray.count
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "sorteCell")
        cell?.textLabel?.text = secondArray[indexPath.row]
        return cell!
    }
}

UPDATE 1: Thanks to @Jay Lee for the above code.

UPDATE 2:

Answer 1

You are not loading the data to the SecondTableViewController instance that is presented on your screen, but to a new SecondTableViewController instance that you created in the func tableView(_:=,cellForRowAt:) method in your FirstTableViewController . The logs are printed from the multiple instances you created from it.

This is not what you want, as you are creating multiple SecondTableViewController instances every time a new cell shows in your FirstTableViewController . You should rather get a reference to the actual SecondTableViewController that is presented and supply the data it.

If you are using a storyboard, you can use prepare(for:sender:) to do that. We have two choices: provide the entire data from the FirstTableViewController to SecondTableViewController using a delegate design pattern, or just provide value to SecondTableViewController and leave the fetching to it. Based on your code, you can just supply the SecondTableViewController with value that your setIndex(value:) method in the SecondTableViewController uses, and get the data after the SecondTableViewController loads.

For example, in your SecondTableViewController :

class SecondTableViewController: UITableViewController {
...
  var detailedValue: String?

  override func viewDidLoad() {
    super.viewDidLoad()
    if let detailedValue = detailedValue {
      setIndex(value: detailedValue)
    }
  }
...
}

and in your FirstTableViewController :

class FirstTableViewController: UITableViewController {
...
  override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    // Set the segue's identifier in the Storyboard
    performSegue(withIdentifier: "yourIdentifier", sender: self)
  }
...
  override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "yourIdentifier" {
      guard let destination = segue.destination as? SecondTableViewController,
            let indexPath = tableView.indexPathForSelectedRow else { return }
      destination.detailedValue = categories[indexPath.row]
    }
  }
}

But note that you already have a data to be shown on SecondTableViewController in your FirstTableViewController , so you should probably make a protocol and set FirstTableViewController its delegate.

EDIT: Your segue should not be connected like this: but like this: