Firebase gives sometimes only parts of my saved values and sometimes everything - swift

Question

I'm trying to code my own messenger. I saved the messages in Firebase database. I'm trying to access the messages with the normal way how I do it every time (database.database().reference().child("users")...., but it gives back only a few messages and only sometimes every message
I already tried it with .childAdded but it doesn't work either
func fetchMessages() {
self.messages.removeAll()
let uid = Auth.auth().currentUser!.uid
let ref = Database.database().reference().child("users").child(uid).child("chats").child(self.chatuid).child("messages")
ref.observeSingleEvent(of: .value) { (snap) in
guard let data = snap.value as? [String: AnyObject] else { return }
//MARK: data = (messageID, AnyObject)
for (messageID, _) in data {
ref.child(messageID).observeSingleEvent(of: .value) { (snap2) in
guard let data2 = snap2.value as? [String: AnyObject] else { return }
//MARK: data2 = ("message": String, "sentuid": String)
guard let message = data2["message"] as? String else { return }
guard let sentuid = data2["sentuid"] as? String else { return }
let messageToAppend = Message(sentuid: sentuid, message: message)
self.messages.append(messageToAppend)
self.messageTableView.reloadData()
}
}
}
}
//self.messages = Place where I save my fetched messages
Firebase-Structure:
{
"users" : {
"V3bLZu61KYTCG0uCWV8LH1f4rRJ3" : {
"chats" : {
"x3GzxwmyLbXrQNNyBF2a82KqrHa2" : {
"messages" : {
"20191014165454" : {
"message" : "Heyho",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"20191014165647" : {
"message" : "Blabla",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"20191014165754" : {
"message" : "Blabla",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"20191014165800" : {
"message" : "Fuchsloch",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"20191014165805" : {
"message" : "Jlksaö",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"20191014165808" : {
"message" : "Jadfsk",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"20191014165811" : {
"message" : "Jskldflsö",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"20191014170041" : {
"message" : "JALSF",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"test" : {
"messange" : "test",
"sentUid" : "MatesForSports"
}
}
}
},
"username" : "Acc2"
},
"x3GzxwmyLbXrQNNyBF2a82KqrHa2" : {
"chats" : {
"V3bLZu61KYTCG0uCWV8LH1f4rRJ3" : {
"messages" : {
"20191014165454" : {
"message" : "Heyho",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"20191014165647" : {
"message" : "Blabla",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"20191014165754" : {
"message" : "Blabla",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"20191014165800" : {
"message" : "Fuchsloch",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"20191014165805" : {
"message" : "Jlksaö",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"20191014165808" : {
"message" : "Jadfsk",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"20191014165811" : {
"message" : "Jskldflsö",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"20191014170041" : {
"message" : "JALSF",
"sentuid" : "V3bLZu61KYTCG0uCWV8LH1f4rRJ3"
},
"test" : {
"messange" : "test",
"sentUid" : "MatesForSports"
}
}
}
},
"username" : "Acc1"
}
}
}
I expected that the code would give back around 10 messages, but it gives sometimes 5, sometimes 3 or even only 2 messages
My firebase-structure of the messages is .child("messages"), then a unique id, then the actual message and the sender at one layer

Answer 1

Here's an an answer followed by a suggestion.
Let's start with replicating your structure using some hard coded values
users
uid_0
chats
chat_uid_0
messages
unique_id_0
msg: "My Message"
sent_uid: "uid_1"
unique_id_1
msg: "Hello, World"
sent_uid: "uid_3"
unique_id_2
msg: "another message"
sent_uid: "uid_2"
then the code to read in the messages, iterate over them and print out the msg and sent_uid
func readMessages() {
let usersRef = self.ref.child("users")
let messagesRef = usersRef.child("uid_0").child("chats").child("chat_uid_0").child("messages")
messagesRef.observeSingleEvent(of: .value, with: { snapshot in
let allMessages = snapshot.children.allObjects as! [DataSnapshot]
for msg in allMessages {
let msgText = msg.childSnapshot(forPath: "msg").value as? String ?? "No Msg"
let sentUid = msg.childSnapshot(forPath: "sent_uid").value as? String ?? "No sender"
print(msgText, sentUid)
}
})
}
and the output is
My message uid_1
Hello, World uid_3
another message uid_2
That being said - your structure is way to deep and should be denormalized. While it may work, as soon as you want to query for items, of find messages posted by a specific user, it just doesn't work.
I don't know your full use case but this would be a better structure
users
uid_0
name: "Hank"
uid_1
name: "Leroy"
chats
uid_0
chat_id_0: true
chat_id_1: true
uid_1
chat_id_5: true
chat_id_0
unique_id_0
msg: "My Message"
sent_uid: "uid_1"
unique_id_1
msg: "Hello, World"
sent_uid: "uid_3"
unique_id_2
msg: "another message"
sent_uid: "uid_2"
With this structure, it's all very shallow and easy to get to data - perform queries etc. You can quickly retreive all chats that uid_0 is involved with, get any messages that uid_3 ever posted or add an observer to uid_1's chat so others are notified when a chat has been added. Again, this is just an example and may not fit your case but it's something to consider.