Observe Single event method returning cached data

[firebase]

Observe Single event method returning cached data

[schmidt-sebastian]

Thanks for sending over this issue. While I understand that this can be frustrating, this is expected behavior. Single even observers will return data from the cache if there is data available. This allows us to fire them immediately. If you use .value observers, you will receive updated data in its second call.

[cbess]

I suppose this makes sense. But, is there a way to do have it pull from the server immediately/initially, without having to call it twice? Am I suppose to use the non-single event methods, then cancel the observer manually?

Also, I would say the documentation should be updated.

[MarksCode]

Any update?

[paulb777]

@MarksCode What kind of update are you looking for? This issue was closed as "expected behavior". stackoverflow is a better place to ask usage questions.

[quanvo87]

Is there a better way of doing this? I've noticed that when using a cache and attempting a singleEvent query, it can take 55-60 attempts before fresh data is returned.

[morganchen12]

@quanvo87 load time is going to depend on the size of the data you're loading and the quality of your internet connection. Are you observing one minute load times for small queries on good internet?

[quanvo87]

@morganchen12 When testing this, I was querying an endpoint that returned a small String. My connection is 15 ping 50/10 down/up. I could probably be more clear--by 55-60 attempts, what I mean is I did a ref.observeSingleEvent, and in the callback, if !snapshot.exists(), print something and repeat the function, until it finally got back data. The print statement executed 50+ times each test run. This is with persistence enabled. With persistence disabled, it just fires once.

[morganchen12]

Oh, I misread your last comment.

With the current API, observing a single event with persistence enabled doesn't let you specify whether you're trying to retrieve cached or server data. The SDK defaults to returning cached data, but this isn't useful if you're trying to retrieve server data. For the time being you should use value listeners instead like Sebastian mentioned above, but this does seem like a non-feature.

[Rahish]

Thanks for sending over this issue. While I understand that this can be frustrating, this is expected behavior. Single even observers will return data from the cache if there is data available. This allows us to fire them immediately. If you use .value observers, you will receive updated data in its second call.

Why in the Second call? As we expect refreshed data whenever we apply the observer to the Database Reference. I tried below code too, its also not refreshing the data
weak var weakSelf = self
valueRef = dbRef?.observe(.value) { (snapShotData) in

            if singleValueObserver
            {
                weakSelf?.dbRef?.removeObserver(withHandle: weakSelf?.valueRef ?? 0)
            }
            weakSelf?.dataFetched(snapShotData)
        }