Parse Cloud - LiveQueries - iOS Client doesn't work

Question

I'm trying to use Parse LiveQueries. I use this Parse "Bootstrap": "https://github.com/parse-community/parse-server",
I can see the logs: info: Create new client: 1,
but I just do not get the update in the query although I have subscribed it. It doesn't even reach the handler of the subscription.handle.

config.json:

{
  "appId": "",
  "masterKey": "",
  "appName": "",
  "cloud": "./cloud/main",
  "databaseURI": "",
  "publicServerURL": "",    

  // Relevant
  "startLiveQueryServer": true,
  "liveQuery": {
    "classNames": ["Channel"]
  },
}

AppDelegate.swift:

// Initialize Parse.
let configuration = ParseClientConfiguration {
    $0.applicationId = self.PARSE_APP_ID
    $0.server = self.PARSE_SERVER
}
Parse.initialize(with: configuration)

AppDelegate.liveQueryClient = ParseLiveQuery.Client()

The Subscription Code (iOS Swift):

public static func listenSubscribedChannels(handler: @escaping (_ channel: Channel) -> Void) {
    var subscription: Subscription<PFObject>?

    let query: PFQuery<PFObject> = PFQuery(className: "Channel").whereKey("subscribers", containedIn: [PFUser.current()!.objectId])

    subscription = AppDelegate.liveQueryClient!.subscribe(query).handle(Event.updated) { _, channel in
        handler(channel)
    }
}

Hypallage

Answer 1

The problem with this code is that you are placing this code var subscription: Subscription<PFObject>? inside the function.

This object must be able to retain it's memory address in order for it to receive events.

For example.

class SomeClass {
    var objects: [PFObject] = []
    var subscription: Subscription<PFObject>?
    var subscriber: ParseLiveQuery.Client!
    let query = PFQuery(className: "Locations")

    func startListener() {
        // initialize the client
        subscriber = ParseLiveQuery.Client()

        // initialize subscriber and start subscription
        subscription = subscriber.subscribe(conversationQuery)

        // handle the event listenrs.
        _ = subscription?.handleEvent({ (_, event) in
            switch event {
            case .created(let object): 
                self.objects.append(object)
                // do stuff 

            default: 
                break // do other stuff or do nothing
            }
        })
    }
}

As you can see from this code, I've placed the variables outside the function definition in order for the Subscription's memory address to be retained.

Wyoming

Update: OK I've just tried that again, and you were right. IDK why it didn't work when I tried it few days ago, maybe made another mistake. Thanks a lot! Yo've earned you 50 points of reputation! :) EDIT: I can award the bounty to you only in 7 hours – Hypallage

You are welcome. The documentation is quite lacking so this is something most misunderstand. Especially since how Firebase's socket works as its memory address still lives even if declared inside a function, (they use a global handler that's why) – Wyoming

Answer 2

You have to register your class before query, like:

Channel.registerSubclass()

Okinawa