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)
    }
}

score 6 · Accepted Answer · answered Jun 23 '17 at 12:45

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.

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 — Etgar, Jun 23 '17 at 13:54
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) — Zonily Jame, Jun 25 '17 at 17:01

score -1 · Answer 2 · answered Jun 01 '17 at 03:32

-1

You have to register your class before query, like:

Channel.registerSubclass()

answered Jun 01 '17 at 03:32

章恩齊

23
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Parse Cloud - LiveQueries - iOS Client doesn't work

2 Answers2

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