Retrieving data from firebase Realtime Datbase with SwiftUI Xcode 11

Question

For a few days I have been trying to read my data from firebase without success. Indeed it is a set of tables also containing tables.

This function is to retrieve the subjects and at the same time the paragraphs

func getSubjects() {
    let subjectRef = database.child("subjects")
    subjectRef.observe(.childAdded, with: { (snapshot) in
        for child in snapshot.children {
            print(snapshot)
             if let snapshot = child as? DataSnapshot,
                let subject = Subject(snapshot.value)
            //subjectList.append(subject)
           // print("Data : \(subject)")
                
        }
    })
}

This is the firebase screen

Console screen

On Android I didn't have this problem, but since I'm new to iOS, I'm having a hard time coping. Any help will be welcome. Thank you

Answer 1

At the moment, you are observing the database for constant changes and it will only run when a child/value has been added into the place you're currently checking, for this you may only want to retrieve a value once, and every time that view is loaded then it will fetch from the database again. It's a lot more efficient and less costly. You may want something like this:

ref = Database.database().reference()
ref.child("subjects").child("0").child("paragraphs").child("0").observeSingleEvent(of: .value, with: { (snapshot) in
        let value = snapshot.value as? NSDictionary
        let location = value["location"] as? NSDictionary
        let title= value?["title"] as? String ?? ""
        let text = value?["text"] as? String ?? ""
        let latitude = location?["latitude"] as? String ?? ""
        let longitude = location?["longitude "] as? String ?? ""
    }) { (error) in
     print(error.localizedDescription)
}

You think each child with nodes inside it as an array, or a json object. You can cast them into an NSDictionary and use that cast to access values inside them if they're nested.

If they're not nested and in the same level as the place you're watching in the database ref, like for instance, above we are looking in the subjects > 0 > paragraphs > 0 node within the database. Title is a value inside that node and not a child so we can simply get the value of title from the database through the data snapshot given back.

I recommend reading the Docs, they're very good and easy to understand when working with different OS/languages.