Save multiple data with a loop in FirebaseDatabase - Swift IOS - ios

Question

with my code I would save multiple data with a loop in my Firebase Database. I have used a while loop to save some strings in my Database but my app saves only the last book and I don't know how to fix this problem. Any ideas?
let refUsers = FIRDatabase.database().reference().child("Users").child("User" + tag_login).child(user_key).child("Books").child("Others")
let key = refUsers.childByAutoId().key
let multipleBooksValues = ["multipleBooks": "Yes", "read": "Yes"] as NSDictionary
refUsers.child(key).setValue(multipleBooksValues)
let refBooks = FIRDatabase.database().reference().child("Books").child("User's books").child(book_key)
var bookNumber = 0
let numberOfBooks = bookList.count
while bookNumber < numberOfBooks {
let book = bookList[bookNumber]
let values = ["book_key\(bookNumber)" : book.book_key!] as NSDictionary
refUsers.child(key).child("multipleBooksNumber").setValue(values)
refBooks.updateChildValues(["onGoingNegotiations" : "Yes", "other_user_key" : self.user_key, "other_tag_login": self.tag_login])
refUsers.child(key).child("multipleBooksNumber").observe(.value, with: { (snapshot) in
let numberChildren = Int(snapshot.childrenCount - 1)
if numberChildren == bookNumber{
bookNumber += 1
}
})
}
Thank you in advance.

Answer 1

Each next book in your loop is overwriting the previous book. The easiest way to prevent this is to call setValue() one level deeper in the tree:
while bookNumber < numberOfBooks {
let book = bookList[bookNumber]
refUsers.child(key).child("multipleBooksNumber/\(bookNumber)").setValue(book.book_key!)
}
Note though that the Firebase documentation and blog recommend against using arrays like this for storing data. Either store the books under their natural key:
refUsers.child(key).child("multipleBooksNumber/\(book.book_key!)").setValue(true)
Or store them under so-called push IDs:
refUsers.child(key).child("multipleBooksNumber").childByAutoId().setValue(book.book_key!);

Answer 2

Maybe the problem is that you save all books to the same path and they are being re-written one by another all the time, so only the last one is being saved in the end?
You specify your key once
let key = refUsers.childByAutoId().key
and then save all values to path
refUsers.child(key).child("multipleBooksNumber").setValue(values)