Variable 'newBalance' captured by a closure before being initialized

Put it simply, I am trying to have a very basic function that takes a user ID and returns the associated balance to that user from a Firestore collection of users.

However, I am getting the following error:

"Variable 'newBalance' captured by a closure before being initialized"

The code is:

func getBalance(uid: String) -> Double {

    var newBalance: Double

    FirebaseManager.shared.firestore.collection("users").document(uid).getDocument{ snapshot, error in
        guard let data = snapshot?.data() else {self.errorMessage = "No data found"
            return}
        let balance = data["balance"] as? Double ?? 0
        print("Function balance \(balance)")
        newBalance = balance

    }

    return newBalance
}

Any help would be appreciated! Thank you!

CodePudding user response：

You need a completion

func getBalance(uid: String,completion:@escaping(Double) -> ()) {

  
    FirebaseManager.shared.firestore.collection("users").document(uid).getDocument{ snapshot, error in
        guard let data = snapshot?.data() else {self.errorMessage = "No data found"
            return}
        let balance = data["balance"] as? Double ?? 0
        print("Function balance \(balance)")
        completion(balance)

    }
 
}

Call

getBalance(uid:<#value#>) { balance in
    print(balance)  
}

OR with SwiftUI use @published

@published var newBalance: Double? 

func getBalance(uid: String) {

  
    FirebaseManager.shared.firestore.collection("users").document(uid).getDocument{ snapshot, error in
        guard let data = snapshot?.data() else {self.errorMessage = "No data found"
            return}
        let balance = data["balance"] as? Double ?? 0
        print("Function balance \(balance)")
        self.newBalance = balance

    }
 
}