Unable to get the Firebase to invoke the observe/observeSingleEvent callback - ios

Question

I want to get a user corresponding to an event
I have a list of Events
let eventsRef = FIRDatabase.database().reference.child("Events")
I have a list of Users
let usersRef = FIRDatabase.database().reference.child("Users")
My Event and User model is as below
Events
Event1
eventHost: user1_uid
Event2
eventHost: user2_uid
Users
User1
email: email1
User2
email: email2
The following callback (in the Event model) is never invoked:
if let userKey = eventData["eventHost"] as? String {
userRef = usersRef.child(userKey)
userRef.observeSingleEvent(of: .value, with: { snapshot in
...
})
}
I can confirm that I have not enabled disk persistence and that user uid is available. Is there anything I am doing obviously wrong?
======
EDIT: The simplified event model
import Foundation
import Firebase
class Event {
// event metadata
private var _eventId: String!
private var _eventHost: User!
var eventId: String {
return _eventId
}
var eventHost: User {
return _eventHost
}
init(eventId: String, eventData: Dictionary<String, Any>) {
self._eventId = eventId
if let userKey = eventData["eventHost"] as? String {
let usersRef = FIRDatabase.database().reference().child("Users")
let userRef = usersRef.child(userKey)
print(userRef)
userRef.observeSingleEvent(of: .value, with: { (snapshot) in
print("USERY: \(snapshot.key)")
if let userDict = snapshot.value! as? Dictionary<String, Any> {
let id = snapshot.key
self._eventHost = User(userId: id, userData: userDict)
}
})
}
}
}
The print(userRef) resolves to
https://xxxx.firebaseio.com/Users/AFHpS3npOga4tfj10GS2HGeT9uJ3`
which is a valid object in my Firebase structure. Snippet of Firebase User structure
"AFHpS3npOga4tfj10GS2HGeT9uJ3" : {
"email" : "test#gmail.com",
"firstName" : "Wilma",
"lastName" : "Flintstone",
"profileImageUrl" : "http://images.iimg.in/c/569f4771c45d324bda8b4660-4-501-0-1453279096/google/user-icon-png-pnglogocom.img",
"provider" : "Firebase",
"userId" : "AFHpS3npOga4tfj10GS2HGeT9uJ3"
},

Answer 1

can you take a look at the rules of your firebase database :
It should be something like this
{
"rules": {
".read": "auth != null",
".write": "auth != null"
}
}
in order to let non authenticated people read / write data you should do the following :
{
"rules": {
".read": true,
".write": true
}
}
From the code you post I don't see any problem ...
If this doesn't work please post more code and tell us what you plan to do exactly so we can better help you.
Edit: To go along with the above suggestion, adding a cancel block to the observe function will reveal if there's a rule issue. If the user cannot access the node, the Xcode console will print 'Permission Denied'
userRef.observeSingleEvent(of: .value, with: { (snapshot) in
print("USERY: \(snapshot.key)")
if let userDict = snapshot.value! as? Dictionary<String, Any> {
let id = snapshot.key
self._eventHost = User(userId: id, userData: userDict)
}
}, withCancel: { error in
print(error.localizedDescription)
})