Firebase & Swift: Performing segue after fetching data

Question

When people log in to my app, I take some data from the database like this:

func DownloadButikker() {
    self.ref?.child("Stores").observe(.childAdded, with: { (snapshot) in
        if let dictionary = snapshot.value as? [String: AnyObject] {
            let store = Store()
            store.Latitude = dictionary["Latitude"]?.doubleValue
            store.Longitude = dictionary["Longitude"]?.doubleValue
            store.Store = dictionary["Store"] as? String
            store.Status = dictionary["Status"] as? String
            stores.append(store)
        }
    })
    self.performSegue(withIdentifier: "LogInToMain", sender: nil)
}

I perform the segue before all data has finished loading. Are there any way to get a completion to the observer or check if all data is loaded before making the segue?

Answer 1

The quick solution is that you need to perform your segue after finishing your async call.

func DownloadButikker() {
    self.ref?.child("Stores").observe(.childAdded, with: { (snapshot) in
        if let dictionary = snapshot.value as? [String: AnyObject] {
            let store = Store()
            store.Latitude = dictionary["Latitude"]?.doubleValue
            store.Longitude = dictionary["Longitude"]?.doubleValue
            store.Store = dictionary["Store"] as? String
            store.Status = dictionary["Status"] as? String
            stores.append(store)
        }
        DispatchQueue.main.async {
          self.performSegue(withIdentifier: "LogInToMain", sender: nil)
        }
    })
}

Answer 2

func DownloadButikker(completion: Bool = false) {
    self.ref?.child("Stores").observe(.childAdded, with: { (snapshot) in
        if let dictionary = snapshot.value as? [String: AnyObject] {
            let store = Store()
            store.Latitude = dictionary["Latitude"]?.doubleValue
            store.Longitude = dictionary["Longitude"]?.doubleValue
            store.Store = dictionary["Store"] as? String
            store.Status = dictionary["Status"] as? String
            stores.append(store)
            completion(true)
        }
    })
}


// In your ViewController
func myFunction() {
   DownloadButikker { (hasFinished) in
      if hasFinished { 
         self.performSegue(withIdentifier: "LogInToMain", sender: nil)
      }
   }
}