Accessing Nested Children in Firebase Database Swift 3 - ios

Question

My current firebase database structure is like this
customer
-L1x2AKUL_KNTKXyza
name:"abc"
subscription
-L1x2AKlvmG0RXv4gL
sub_no: "123"
sub_name: ""
-L1x2AKlvmG0RXv4ab
sub_no: "456"
sub_name" ""
-L1x2AKUL_KNTKXymk
name:"xyz"
subscription
-L1x2AKlvmG0RXv4xy
sub_no: "789"
sub_name: ""
I am trying to access all subcriptions of all customer records at once.
This is the code I am using:
var ref: DatabaseReference!
ref = Database.database().reference(withPath: "customer")
ref.observe(.value, with: { snapshot in
let enumerator = snapshot.children
while let rest = enumerator.nextObject() as? DataSnapshot {
let imageSnap = rest.childSnapshot(forPath: "subscription")
let dict = imageSnap.value as! NSDictionary
//self.vehicleListDict.append(dict.object(forKey: "sub_no") as! NSDictionary)
print("value : \(dict)")
}
print("vehicleListDict : \(self.vehicleListDict)")
}) { (error) in
print(error.localizedDescription)
}
I am unable to access all the subscriptions within all customer records at once. Its only accessing till one level. I tried to put a while loop within the while that exists but that also does not give me the output needed. It goes in an infinite loop instead. Please could anyone help. I am using firebase realtime database for the first time.
The fetched values should be
123
456
789

Answer 1

The code for doing specifically what you are asking is
let customerRef = self.ref.child("customer")
customerRef.observe(.childAdded, with: { snapshot in
let subscriptionSnap = snapshot.childSnapshot(forPath: "subscription")
for child in subscriptionSnap.children {
let snap = child as! DataSnapshot
let dict = snap.value as! [String: Any]
let subNo = dict["sub_no"] as! String
print(subNo)
}
})
and the output is
a123
a456
a789
*note that I am reading the sub_no as a STRING which is why I added 'a' in front. If they are actually integers change the line to
let subNo = dict["sub_no"] as! Integer
*note2 this will leave a .childAdded observer to the main node in question so any further children that are added will fire the code in the closure.
Edit:
If you want to just retrieve all of the data at one time and not leave a childAdded observer then this will do it:
let customerRef = self.ref.child("customer")
customerRef.observeSingleEvent(of: .value, with: { snapshot in
for customerChild in snapshot.children {
let childSnap = customerChild as! DataSnapshot
let subscriptionSnap = childSnap.childSnapshot(forPath: "subscription")
for subscriptionChild in subscriptionSnap.children {
let snap = subscriptionChild as! DataSnapshot
let dict = snap.value as! [String: Any]
let subNo = dict["sub_no"] as! String
print(subNo)
}
}
})
and the output is
a123
a456
a789