Data is not displayed in TableView from Firebase - swift

Question

I have a 2 problems with displaying data in a table from Firebase.
Nothing displayed in TableView from Firebase
I I can not add a link(child) to a variable
Print is working. I get access to Firebase, but nothing is added to TableView. Please, look at my code and correct where i'm wrong.
It's my model
class Exercises {
var titleExercise = ""
var descriptionExercise = ""
init (titleExercise: String, descriptionExercise: String) {
self.titleExercise = titleExercise
self.descriptionExercise = descriptionExercise
}
}
It's my ViewController
class ExercisesViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
//MARK: Properties
var refWorkout: String = ""
var workout: TrainingProgram?
var ref: DatabaseReference!
#IBOutlet weak var tableView: UITableView!
var exercises = [Exercises]()
//MARK: Methods
override func viewDidLoad() {
super.viewDidLoad()
fetchExercises()
tableView.dataSource = self
tableView.delegate = self
refWorkout = workout!.title
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return exercises.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! ExercisesTableViewCell
let workouts = exercises[indexPath.item]
cell.titleLabel.text = workouts.titleExercise
cell.descriptionLabel.text = workouts.descriptionExercise
return cell
}
func fetchExercises() {
Database.database().reference().child("programs").child("OPEN SPACE").child("exercises").observe(.childAdded) { (snapshot) in
print(snapshot.value)
if let dict = snapshot.value as? [String: AnyObject] {
let newTitle = dict["title"] as! String
let newDescription = dict["description"] as! String
let exerciseTableCell = Exercises(titleExercise: newTitle, descriptionExercise: newDescription)
}
}
DispatchQueue.main.async {
self.tableView.reloadData()
}
}
}
And I have second question. It also addresses this issue.
As you can see, I have refWorkout = workout!.title Here comes the title from previous ViewController , and refWorkout is a child for Firebase. If I will write next code
ref = Database.database().reference().child("programs").child(refWorkout).child("exercises")
ref.observe(.childAdded) { (snapshot) in
print(snapshot.value)
}
Everything will work. Print will work. But if I insert this code to func fetchExercises() - > It will look like
func fetchExercises() {
Database.database().reference().child("programs").child(refWorkout).child("exercises").observe(.childAdded)...
My app crashed.
Please help me with two questions. Thank you!
My Firebase structure

Answer 1

This is a common mistake, you are reloading the table view too soon and you don't assign/append the result to the data source array
The observe API works asynchronously, put the line to reload the table view into the closure
func fetchExercises() {
Database.database().reference().child("programs").child("OPEN SPACE").child("exercises").observe(.childAdded) { (snapshot) in
print(snapshot.value)
if let dict = snapshot.value as? [String: Any] { // most likely all values are value type
let newTitle = dict["title"] as! String
let newDescription = dict["description"] as! String
let exercise = Exercises(titleExercise: newTitle, descriptionExercise: newDescription)
self.exercises.append(exercise)
}
DispatchQueue.main.async {
self.tableView.reloadData()
}
}
}
Side note:
You class contains 3 bad practices:
Semantically objects used in collection types should be named in singular form.
Don't declare properties with default values if there is an initializer.
There is too much redundant information in the variable names
And in most cases a struct and even constants are sufficient. I'd recommend
struct Exercise {
let title : String
let description : String
}
In a struct you get the initializer for free.