How to know if a Firebase has fetched a value - ios

Question

I have three functions getNewOrder(),storeOrderDetails(_ details:[String:String]) and getUserInfo(_ userID:String).
Function getNewOrder() is called first. It fetches new orders ( .childAdded values) and sends the dictionary to storeOrderDetails(_ details:[String:String]).
storeOrderDetails(_ details:[String:String])then segregate all the values and callsgetUserInfo(_ userID:String)` by passing it userID which was present in its details.
getUserInfo(_ userID:String) then fetches users details and returns user's
information.
However, the problem is [ userInfo = getUserInfo(_ userID:String) in storeOrderDetails(_ details:[String:String]) ] userInfo is always empty. Apparently func getUserInfo(_ userID:String) goes into a completion block after it has returned empty value.
I want these three functions to execute in sequential way.
Any advice is highly appreciated.
Please follow the below Links to review my code.
https://imgur.com/hNjvyDk
https://imgur.com/J0LMXMg
func childAdded(){
let ref = Database.database().reference().child("Orders").child(todaysDate)
ref.observe(.childAdded) { (snapshot) in
var details = [String:String]()
if let orderID = snapshot.key as? String {
ref.child(orderID).observeSingleEvent(of: .value, with: { (snap) in
self.newOrderTextView.text = ""
self.customerNameLabel.text = ""
self.customerPhoneLabel.text = ""
self.orderNumberLabel.text = ""
let enumerator = snap.children
while let rest = enumerator.nextObject() as? DataSnapshot {
details[rest.key as? String ?? ""] = rest.value as? String ?? ""
}
self.storeUserDetails(details)
})
}
}
}
func storeUserDetails(_ details:[String:String]){
if details["CustomerID"] != nil {
userInfo = getUserDetails(details["CustomerID"]!)
print(userInfo)
}
if !userInfo.isEmpty{
let order = OrderDatabase()
order.customerEmail = userInfo["Email"]!
order.customerName = userInfo["Name"]!
order.orderAcceptStatus = details["OrderStatus"]!
order.customerOrderNumber = details["orderNumber"]!
order.orderID = details["orderID"]!
order.time = details["Time"]!
order.customerFirebaseID = details["CustomerID"]!
self.orderDatabase[details["orderNumber"]!] = order
self.orderTable.reloadData()
}
}
func getUserDetails(_ userID:String) -> [String:String]{
var details = [String:String]()
let userDetailsReference = Database.database().reference().child("Users")
userDetailsReference.child(userID).observeSingleEvent(of: DataEventType.value, with: { (snapshot) in
if let dictionary = snapshot.value as? NSDictionary {
self.customerNameLabel.text = dictionary.value(forKey: "Name") as? String
self.customerPhoneLabel.text = dictionary.value(forKey: "Email") as? String
details["Name"] = dictionary.value(forKey: "Name") as? String
details["Email"] = dictionary.value(forKey: "Email") as? String
}
})
return details
}

Answer 1

From what I can see here, I am betting that the issue you are facing has to do with the fact that the methods are asynchronous. So one thing is not completely finished and some other method gets fired too soon. There are a few ways to deal with this issue. One is completion handlers, and the other is adding observers. Below is an example of doing both for Firebase. Here I'm asking a getLocationPhotos method to get all the photos from Firebase. Notice the observers and completion handler
func getLocationPhotos(coordinate:CLLocationCoordinate2D){
dbHandler.getImageFileNames(coordinateIn: coordinate) { (filenames) in
if filenames.isEmpty {
log.debug(String.warningGet + "filenames is empty")
return
}//if filenames.isEmpty
self.imageFiles = filenames.filter { $0 != "none" }
if self.imageFiles.isEmpty {
log.error(String.errorGet + "imageFiles array is empty")
return
}//if imageFiles.isEmpty
for file in self.imageFiles {
let reference = self.storageHandler.imageReference.child(file)
let download = self.imageView.sd_setImage(with: reference)
if let i = self.imageView.image {
self.imageArray.append(i)
self.collectionView.reloadData()
}//let i
download?.observe(.progress, handler: { (snapshot) in
guard let p = snapshot.progress else {
return
}//let p
self.progressView.progress = Float(p.fractionCompleted)
if self.progressView.progress == Float(1) {
self.progressView.isHidden = true
}
})//progress
download?.observe(.success, handler: { (snapshot) in
self.progressView.progress = 1
self.progressView.isHidden = true
self.collectionView.setNeedsLayout()
})//success
download?.observe(.failure, handler: { (snapshot) in
log.error(String.errorGet + "Error occured getting data from snapshot")
})//failure
}//for file
}//dbHandler