Strange behaviour on Firebase query result SWIFT - ios

Question

I'm getting this error on the line let itemToAdd = snapshot.childSnapshot(forPath: "Shopa function that retrieves data from Firebase.
the output of the console in Could not cast value of type 'NSNull' (0x1118c8de0) to 'NSString' (0x10dda45d8)..
What I'm trying to do is to filter database ordering by one value
opening Timeand than get another value Shop Namefrom the returned entries in the snapshot.
here's the function:
func filterOpenShops(enterDoStuff: #escaping (Bool) -> ()) {
ref = Database.database().reference().child("Continent").child("Europe").child("Country").child("Italy").child("Region").child("Emilia-Romagna").child("City").child("Bologna").child("Shops").child("Shops Opening Times")
let query = ref?.queryOrdered(byChild: "Opening Time").queryStarting(atValue: openingTimeQueryStart).queryEnding(atValue: openingTimeQueryEnd)
query?.observe(.value, with: { (snapshot) in
for childSnapshot in snapshot.children {
// new modification
if childSnapshot is DataSnapshot {
let itemToAdd = snapshot.childSnapshot(forPath: "Shop Name").value as! String // gets the open shop from snapshot
self.availableShopsArray.append(itemToAdd)
print(snapshot.children)
print(" Open Shops are \(self.availableShopsArray)")
}
}
// still asynchronous part
enterDoStuff(true)
// call next cascade function filterClosedShops only when data
})
// Sychronous part
print("opening query start is \(openingTimeQueryStart) and opening query end is \(openingTimeQueryEnd)")
} // end of filterOpenShops()
EDIT:
I rewrote the function as:
func filterOpenShops(enterDoStuff: #escaping (Bool) -> ()) {
// get from Firebase snapshot all shops opening times into an array of tuples
//shopOpeningTimeArray:[(storeName: String, weekdayNumber: String, opening1: Sring, closing1: String, opening2:String, closing2: String)]
ref = Database.database().reference().child("Continent").child("Europe").child("Country").child("Italy").child("Region").child("Emilia-Romagna").child("City").child("Bologna").child("Shops").child("Shops Opening Times")
let query = ref?.queryOrdered(byChild: "Opening Time").queryStarting(atValue: String(describing: openingTimeQueryStart)).queryEnding(atValue: String(describing :openingTimeQueryEnd))
query?.observe(.value, with: { (snapshot) in // original is ok
// guard let data = snapshot.value as? [String:String] else { return }
for childSnapshot in snapshot.children {
print("snapshot is: \(childSnapshot)")
print("snapshot.childrend is: \(snapshot.children)")
guard let data = snapshot.value as? [String:String] else { return }
let itemToAdd = data["Shop Name"]
self.availableShopsArray.append(itemToAdd!)
print("Open Shop is: \(String(describing: itemToAdd))")
print(" Open Shops are \(self.availableShopsArray)")
}
// still asynchronous part
enterDoStuff(true)
// call next cascade function filterClosedShops only when data
print(" Open Shops are \(self.availableShopsArray)")
})
print("opening query start is \(openingTimeQueryStart) and opening query end is \(openingTimeQueryEnd)")
} // end of filterOpenShops()
but I still get a null object and not a [String:String] as expected.
The function that created the entries in Firebase is:
func postOpeningTime() {
// if shopNameTextfield.text != nil && openingTimeTextfield.text != nil && closingTimeTextfield.text != nil {
let shopName = shopNameTextfield.text!
let openingTime = openingTimeTextfield.text!
let closingTime = closingTimeTextfield.text!
// } else {return}
let post: [String:String] = [
"Shop Name" : shopName ,
"Opening Time" : openingTime ,
"Closing Time" : closingTime
]
var ref: DatabaseReference!
ref = Database.database().reference()
ref?.child("Continent").child("Europe").child("Country").child("Italy").child("Region").child("Emilia-Romagna").child("City").child("Bologna").child("Shops").child("Shops Opening Times").childByAutoId().setValue(post)
}
Now I have two behaviours:
1st: When querying for entries and finds values that are Int: completion get called but I get no snapshot print.
2nd: When querying for entries and find values that are String: completion doesn't get called but snapshot prints the right entries with values.
Can anyone please spot what's going on here?

Answer 1

I found the problem to bee the way I was casting query result.
Casting it as [String:String] produced to return because upshot was actually [String[String:String]] when all the values for entry's parameter were String, but as I changed Opening Time and Closing time to be Int, than I have to read the snapshot as [String[String:Any]].
So the final function is:
func filterOpenShops(setCompletion: #escaping (Bool) -> ()) {
// Empty the array for beginning of the search
self.availableShopsArray.removeAll()
var ref = Database.database().reference()
ref.child("Continent").child("Europe").child("Country").child("Italy").child("Region").child("Emilia-Romagna").child("City").child("Bologna").child("Shops").child("Shops Opening Times").queryOrdered(byChild: "Opening Time").queryStarting(atValue: openingTimeQueryStart).queryEnding(atValue: openingTimeQueryEnd).observe(.value) { (snapshot) in
print(snapshot)
if let data = snapshot.value as? [String : [String : Any]] {
for (_, value) in
data {
let shopName = value["Shop Name"] as! String
let active = value["Active"] as! String
if active == "true" {
self.availableShopsArray.append(shopName)
print("Shop_Name is :\(shopName)")
print("self.availableShopsArray is: \(self.availableShopsArray)")
}
}
} else {
print("No Shops")
}
// still asynchronous part
setCompletion(true)
// call next cascade function filterClosedShops only when data retrieving is finished
self.filterClosedShops(setCompletion: self.completionSetter)
print(" 1 Open Shops are \(self.availableShopsArray)")
}
} // end of filterOpenShops()