Fetching data from Firebase database?

Question

I have this code that I want to load some data from FirebaseDatase

func fetchVinylsData(){
    SVProgressHUD.show()
    guard let currentUID = Auth.auth().currentUser?.uid else { return }

    dbRef.child("vinyls").child(currentUID).observe(.childAdded) { (snapshot) in
        guard let dictionary = snapshot.value as? Dictionary<String,AnyObject> else { return }
        let vinyl = Vinyl(dictionary: dictionary)
        print(dictionary)
        self.vinyls = [Vinyl]()
        self.vinyls.append(vinyl)
        self.vinyls.sort(by: { (vinyl1, vinyl2) -> Bool in
            return vinyl1.artist < vinyl2.artist
        })
        self.tableView.reloadData()
    }
    SVProgressHUD.dismiss()
}

when I print dictionary I get all the records fine but my tableview does not get populated.I was working fine until I decided to add a new field to Vinyl.swift. The structure at firebase database is without the new field.is this a problem? Here is the code for Vinyl.swift:

import UIKit
import Firebase

class Vinyl {
    var vinylID : String!
    var title : String!
    var artist : String!
    var label : String!
    var vinylCountry : String!
    var isOut : Bool = false
    var vinylLocation : String!
    var year : String!
    var vinylAutoID : String!
    var vinylFormat : String!

    init(dictionary : Dictionary<String,AnyObject>) {
        guard let title = dictionary["title"] as? String else { return }
        guard let artist = dictionary["artist"] as? String else { return }
        guard let label = dictionary["label"] as? String else { return }
        guard let vinylID = dictionary["vinylID"] as? String else { return }
        guard let vinylCountry = dictionary["vinylCountry"] as? String else { return }
        guard let vinylLocation = dictionary["vinylLocation"] as? String else { return }
        guard let year = dictionary["vinylYear"] as? String else { return }
        guard let autoID = dictionary["autoID"] as? String else { return }
        guard let isOut = dictionary["isOut"] as? Bool else { return }
        guard let vinylFormat = dictionary["format"] as? String else { return }

        self.vinylID = vinylID
        self.title = title
        self.artist = artist
        self.label = label
        self.vinylCountry = vinylCountry
        self.isOut = isOut
        self.vinylLocation = vinylLocation
        self.year = year
        self.vinylAutoID = autoID
        self.vinylFormat = vinylFormat
    }
}

Answer 1

I would not suggest to use guard let in your init method because suppose dictionary["title"] is empty or not available then it will return from the first line of your code and same will happen for others. And to solve this issue you can use Nil-Coalescing Operator (Means you can assign default value nil or any other value if something["something"] is nil or optional )

Replace

guard let title = dictionary["title"] as? String else { return }
guard let artist = dictionary["artist"] as? String else { return }
guard let label = dictionary["label"] as? String else { return }
guard let vinylID = dictionary["vinylID"] as? String else { return }
guard let vinylCountry = dictionary["vinylCountry"] as? String else { return }
guard let vinylLocation = dictionary["vinylLocation"] as? String else { return }
guard let year = dictionary["vinylYear"] as? String else { return }
guard let autoID = dictionary["autoID"] as? String else { return }
guard let isOut = dictionary["isOut"] as? Bool else { return }
guard let vinylFormat = dictionary["format"] as? String else { return }

with

let title = dictionary["title"] as? String ?? ""
let artist = dictionary["artist"] as? String ?? ""
let label = dictionary["label"] as? String ?? ""
let vinylID = dictionary["vinylID"] as? String ?? ""
let vinylCountry = dictionary["vinylCountry"] as? String ?? ""
let vinylLocation = dictionary["vinylLocation"] as? String ?? ""
let year = dictionary["vinylYear"] as? String ?? ""
let autoID = dictionary["autoID"] as? String ?? ""
let isOut = dictionary["isOut"] as? Bool ?? false
let vinylFormat = dictionary["format"] as? String ?? ""

And you also need to update your UI in main queue when you are working with async calls like shown below:

DispatchQueue.main.async {
    self.tableView.reloadData()
}