How to retrieve an int-type data from firebase to xcode? (Error: Cannot convert value of type 'String' to expected argument type 'Int') - swift

Question

I was trying to fetch data from firebase to my xcode project. The only fields I have are 'userName', 'age', and 'number'. I was trying to append the values into arrays userNames, ages, and numbers. However, I get the error Error: Cannot convert value of type 'String' to expected argument type 'Int in the appending age and number lines. They both have been entered as Int types in the database.
I thought about converting the values of the database into Int types since I think Xcode is taking them as String types? I tried, but I think my code itself was wrong so I couldn't solve it. I would appreciate the help!
func fetchData () {
let database = Firestore.firestore()
database.collection("users").addSnapshotListener {(snap, Error) in
if Error != nil {
print("Error")
return
}
for i in snap!.documentChanges {
let documentID = i.document.documentID
let userName = i.document.get("userName")
let age = i.document.get("age")
let number = i.document.get("number")
DispatchQueue.main.async {
self.userNames.append("\(userName)")
self.ages.append("\(Int(age))") // error line
self.numbers.append("Int\(number)") // error line
}
}
}
}

Answer 1

You can try to coerce the data into the types you want by using as?. (get returns Any? by default)
let userName = i.document.get("userName") as? String
let age = i.document.get("age") as? Int
let number = i.document.get("number") as? Int
Keep in mind that you'll end up with Optional values, so you'll need to have a fallback in case you don't get the type you expect.
If you wanted to provide defaults, you could do:
let userName = i.document.get("userName") as? String ?? ""
let age = i.document.get("age") as? Int ?? 0
let number = i.document.get("number") as? Int ?? 0
Then, later:
self.userNames.append(userName)
self.ages.append(age)
Note that your compilation errors were happening because you were trying to store String values ("") in an [Int]
In general, rather than storing all of these in separate arrays, you may want to look into making a struct to represent your data and storing a single array with that type. See this answer for an example: https://stackoverflow.com/a/67712824/560942
And, the Firestore documentation on custom objects: https://firebase.google.com/docs/firestore/manage-data/add-data#custom_objects