Retrieve firebase data where users root collection references a sibling collection - ios

Question

Accessing all maps works perfectly in Firebase with this path, however it grabs all maps available in the "Maps" root collection.
let yourMapRef = Database.database().reference().child("Maps")
I am trying to only access the maps that the user is part of. I have therefore tried to follow stack questions and firebase tutorials but i cant grasp how to do this.
For example i would like Adam to only grab his moderated maps by
let yourMapRef = Database.database().reference().child("users/\(userProfile.uid)/Maps")
How should i think around this problem and how can this be solved?
Users (root collection structure)
{
"4g99cMTM4begwooORsO4EKNV456" : {
"username" : "Adam",
"Maps" : {
"-LpYo_pQ8zIOGHHlNU1Q" : true
}
},
"6g55cHXH4begwooHQvO4EKNV3xm1" : {
"username" : "Ellen",
"Maps" : {
"-LpY4XEER-b21hwMi9sp" : true
}
}
}
Maps (root collection structure)
{
"-LpY4XEER-b21hwMi9sp" : {
"mapmoderators" : {
"6g55cHXH4begwooHQvO4EKNV3xm1" : true
},
"mapphotoURL" : "https://firebasestorage.googleapis.com/v0/b/...",
"mapusername" : "Hello World"
},
"-LpYo_pQ8zIOGHHlNU1Q" : {
"mapmoderators" : {
"4g99cMTM4begwooORsO4EKNV456" : true
},
"mapphotoURL" : "https://firebasestorage.googleapis.com/v0/...",
"mapusername" : "Dream"
}
}

Answer 1

So what you want to do is get the users first, then use it against the maps collection to check wether they moderate a map or not:
func getUsers() {
let userRef = Database.database().reference().child("users").child(currentUserID)
userRef.observeSingleEvent(of: .value, with: { (snapshot) in
let root = snapshot.value as? Dictionary
if let mapsByUser = root["Maps"] as? [String: Bool] {
for (documentId, status) in mapsByUser {
if status {
// Document is true, check for the maps
self.getMaps(key: documentId, owner: currentUserID)
}
}
}
}) { (error) in
print(error.localizedDescription)
}
}
// Check for maps
func getMaps(key:String, owner:String) {
let userRef = Database.database().reference().child("maps").child(key)
userRef.observeSingleEvent(of: .value, with: { (snapshot) in
let user = snapshot.value as? Dictionary
if let mapsByUser = user["mapmoderators"] as? [String: Bool] {
for (userId, status) in mapsByUser {
if userId == owner && status == true {
print("Owner \(owner) manages this \(user)")
}
}
}
}) { (error) in
print(error.localizedDescription)
}
}
Call getUsers() on viewDidLoad to test this.