Can't get value of node in Firebase - ios

Question

I read a lot examples and most of them have old style (even they are written current year). Please help understand where my code is wrong? It is built but I can't get a value 123456.
import UIKit
import Firebase
class ViewController: UIViewController {
#IBOutlet weak var val_txt: UITextField!
let ref = FIRDatabase.database().reference()
var barcode = 0
override func viewDidLoad() {
super.viewDidLoad()
FIRAuth.auth()?.signIn(withEmail: "*****#gmail.com", password: "*****", completion: {(user,error) in print("Авторизация Ок!!!")})
}
#IBAction func getData_btn(_ sender: Any) {
ref.child("goods").child("1").observe(FIRDataEventType.value, with: {(snapshot) in
let postDict = snapshot.value as? [String:AnyObject] ?? [:]
print(postDict["barcode"] as? Int)
})
print(barcode)
}
I've change code in order to understand Does print execute and I found that it doesn't
print("Method started")
ref.child("goods").child("1").observe(FIRDataEventType.value, with:{(snapshot) in
let postDict = snapshot.value as? [String:AnyObject] ?? [:]
print("Method is executing")
})
print("Method completed")
And I get just two rows of print
"Method started"
"Method completed"

Answer 1

If you want value only for "1":
var ref: FIRDatabaseReference!
ref = FIRDatabase.database().reference()
ref.child("goods").child("1").observeSingleEvent(of: .value, with: { (snapshot) in
let id = snapshot.childSnapshot(forPath: "barcode")
print(id)
})
but if you want all barcodes:
var ref: FIRDatabaseReference!
ref = FIRDatabase.database().reference()
ref.child("goods").observeSingleEvent(of: .value, with: { (snapshot) in
if let snapshots = snapshot.children.allObjects as? [FIRDataSnapshot] {
for snap in snapshots
{
let barcode = snap.childSnapshot(forPath: "barcode").value! as! String
print(barcode)
}
}
})

Answer 2

In your code let ref = FIRDatabase.database().reference() do not Point to reference URL because during initialization your firebase not configure in your app delegate file (Not called FIRApp.configure()).
So put in func viewDidLoad() as follow:
import UIKit
import Firebase
class ViewController: UIViewController {
#IBOutlet weak var val_txt: UITextField!
let ref:FIRDatabaseReference!
var barcode = 0
override func viewDidLoad() {
super.viewDidLoad()
ref:FIRDatabaseReference = FIRDatabase.database().reference()
FIRAuth.auth()?.signIn(withEmail: "*****#gmail.com", password: "*****", completion: {(user,error) in print("Авторизация Ок!!!")})
}

Answer 3

Use below code it will help you.
let ref = FIRDatabase.database().reference()
ref.child("goods").child("1").observe(DataEventType.value, with: {(snapshot) in
if snapshot.childrenCount>0 {
for transactions in snapshot.children.allObjects as! [DataSnapshot] {
var obj = transactions.value as! [String:AnyObject]
print(obj["barcode"] as! Int)
}
}
})