SwiftUI Firebase RealTime Database doesn't retrieve value

Question

florian1744 OP

Created Mar ’20

Replies 2

Boosts 0

Views 2.6k

Participants 2

Hey,

I'm a beginner hobby dev who tried cloud storage for first time using SwiftUI.

I wanted to make a simple app which only needs to retrieve some values of a Database.

I'm using Firebase RealTime Database.

My Database structure looks like this:

monsterhunter-e8167

Velkhana
- HP: 12000
- element: Ice
Rath
- HP: 8000
- element: Fire

My Code looks like this:

import SwiftUI
import FirebaseDatabase


struct ContentView: View {

    var ref: DatabaseReference = Database.database().reference()
    var body: some View {
        Button(action: {
            self.ref.child("monsterhunter-e8167").child("Velkhana")
                .observeSingleEvent(of: .value, with: { (snapshot) in
      
              let value = snapshot.value as? NSDictionary
              let hp = value?["HP"] as? Int ?? 0
    
              print(hp)

              // ...
              }) { (error) in
                print(error.localizedDescription)
            }
        }) {
            Text("print")
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

However it is printing out

the expected output should be:

I figured out "value" is nil but I don't know why.

"childpath" should be correct

Can anyone tell me what I'm doing wrong?

Boost

Answer 1

Claude31 OP

Mar ’20

You mean line 16 prints 0 ?

That effectively means :

value?["HP"] as? Int

is nil.

Could you add a print on line 15:

print("snapshot.value", snapshot.value)
print("value", value)
print("value?[HP]", value?["HP"])

From Firebase doc, I read that you get an NSNumber, not an Int.

So, may be (I'm not practicing Firebase, so take it with some precaution) you should write

var hp = 0
let number : NSNumber? = value?["HP"] as? NSNumber
if let integerValue = number?.intValue {
    hp = integerValue
}

0

Answer 2

florian1744 OP

Mar ’20

thanks for the reply.

The output of the print statements showed me the following things:

snapshot.value Optional()
value nil
value?[HP] nil

Also I added the other piece of code. The output was also

0