Swift - How to fetch next data if value changes - swift

Question

I am trying to fetch next question from server after the previous one is played by users.
When arrayNum is changed, can't fetch the next question. I am thinking to use switch method to write same code over and over again. Is there a better way?
func retriveRoom(){
let idRef = db.collection("ROOMS_Collection").document(GameData.shared.documentID)
idRef.getDocument { (docSnapshot, error) in
guard let docSnapshot = docSnapshot, docSnapshot.exists else {return}
guard let data = docSnapshot.data() else { return }
let questionID = data["questionID"] as? Array<Int>
let questionRef = self.db.collection("QUESTIONS_Collection").document("\(questionID![self.arrayNum])")
questionRef.getDocument{ (docSnapshot, error) in
guard let docSnapshot = docSnapshot, docSnapshot.exists else { return }
let data = docSnapshot.data()
self.questionArray = (docSnapshot.data()?.compactMap({_ in Question(dictionary: data!)}))!
let question = self.questionArray[0]
self.answer = Int(question.answer)!
self.questionText.fontColor = UIColor.white
self.questionText.fontName = "Verdana"
self.questionText.text = ("\(question.question)")
self.questionText.fontSize = 24.0
self.questionText.numberOfLines = 0
self.questionText.lineBreakMode = NSLineBreakMode.byWordWrapping
self.questionText.zPosition = 5
self.questionText.position = CGPoint(x: (self.questionBackground?.frame.midX)! - 5, y: (self.questionBackground?.frame.midY)! - 5)
self.questionText.preferredMaxLayoutWidth = (self.questionBackground?.frame.width)! - 10
self.addChild(self.questionText)
}
}
}

Answer 1

If I understand what you are trying to do correctly, you want to fetch another question from your database when arrayNum changes. I think your best bet is to try a property observer function on your arrayNum variable. Something like this:
In your class declaration where you declare arrayNum:
var arrayNum : Int {
didSet {
// Implement retrieveRoom() here
retrieveRoom()
}
}
What is not clear from your code is exactly when and how arrayNum changes. As an alternative to didSet you can also use willSet, which, as the name suggests, is called when a parameter value is about to be reassigned. You can read up on this here:
https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Properties.html
(And by the way, it might serve your user experience better if you were to fetch a batch of questions in one go rather than repeat the database call every time a new question is required. But that is not strictly relevant to your question.)
Hope that helps.