Read Array from Firebase - Swift

Question

I am writing a function that allows me to read the data inside the Database. I can read the String from Firebase but I cannot read the arrays. I tried like this but it doesn't work:

func fetchData(collection: String) { 
    DatabaseFirestore.collection(collection).addSnapshotListener { (querySnapshot, error) in 
        guard let documents = querySnapshot?.documents else {
            print("No documents") 
            return
        }
        self.example = documents.map { (queryDocumentSnapshot) -> Example in
            let data = queryDocumentSnapshot.data()
            let ex1 = data["ex1"] as? String ?? "" // it is not an array in the database
            let ex2 = data["ex2"] as? String ?? "" // is an array in the database
            return Example(ex1: ex1, ex2: ex2)
        }
    }
}

How could I change this line so that it reads the array inside the database?

let ex2 = data["ex2"] as? String ?? ""

as? [Any] instead of as? String? But it's unclear what you need exactly since you are mixing Array & String. — Larme
– Larme, Commented Aug 2, 2022 at 19:02
ex1 is a String, ex2 is an array of strings within the database. I'm looking for a way to save it in variables. — mickele29
– mickele29, Commented Aug 2, 2022 at 19:05
if you cannot understand the difference between a String and an array of String, [String], then it's time to read the basics again at: docs.swift.org/swift-book/LanguageGuide/TheBasics.html — workingdog support Ukraine
– workingdog support Ukraine, Commented Aug 2, 2022 at 23:34

Yuliia Sorokopud · Accepted Answer · 2022-08-02 21:25:59Z

0

Casting as [String] instead of String might fix the issue

 You also could check this answer - it could be helpful when retrieving arrays and dictionaries from Firebase

edited Aug 2, 2022 at 21:25

answered Aug 2, 2022 at 21:25

Yuliia Sorokopud

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2 Comments

mickele29 Over a year ago

If I write " let ex2 = data["ex2"] as? [String] ?? "" " gives this error: Cannot convert value of type 'String' to expected argument type '[String]'. I tried to change it to this: " let ex2 = data["ex2"] as? [String] ?? [ ] ", and when I return the value I write: " return Example(ex1: ex1, ex2: ex2 as Any as! [String]) ". If in the database there are no values related to "ex2", and I try to print the value the app crashes. How can you make sure that if it finds no "ex2" value, it takes an empty string as a value? I also tried this: let ex2 = data["ex2"] as? [String] ?? [ ""]

workingdog support Ukraine Over a year ago

With let ex2 = data["ex2"] as? [String] ?? [], use Example(ex1: ex1, ex2: ex2). Read the basics again, it will tell you, doing this: Example(ex1: ex1, ex2: ex2 as Any as! [String]) is crazy.

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