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

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" : "[email protected]", "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" },

I want to help, but I don't see anything that is obviously wrong. I assume when you say the callback is never invoked, you put a breakpoint in it? — Jen Person
– Jen Person, Commented May 9, 2017 at 16:12
@JenPerson Yes I put a breakpoint in, and it does not get there — avinash
– avinash, Commented May 9, 2017 at 16:15
If you print something in your observe function, will that execute? — J. Doe
– J. Doe, Commented May 9, 2017 at 16:15
@J.Doe No, it is not going in at all. I do see it print once in a while, but have been unable to put a finger on how to get it to do consistently — avinash
– avinash, Commented May 9, 2017 at 16:19
More information is needed: Does the if let userKey = code get called? If you put a breakpoint at self._eventId and manually step through the code, one line at a time, on what line does it stop working? — Jay
– Jay, Commented May 9, 2017 at 17:27

Jay · Accepted Answer · 2017-05-09 19:29:22Z

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) })

Yes, it is set to let non authenticated people read/write data. I have edited the post to include the relevant/simplified parts of the event model. The complete code is posted here
your code is correct , could you try to add keepSynced(true) and execute again ?
I believe that is only when you have persistence enabled? In either case, adding it does not help

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