Hey all, so I want to prevent making duplicate requests to a server. Does it make sense to store a b...

# coroutines

[bsimmons]

Hey all, so I want to prevent making duplicate requests to a server. Does it make sense to store a bunch of Deferred<T> s and reuse them? Or is this a coroutine anti-pattern? I'm pretty new to coroutines so I'm just wonder if there is a better way.

private val notesDeferred = HashMap<String, Deferred<Resource<String>>>()
suspend fun getNotes(id: String): Resource<String>{
    if(notesDeferred.containsKey(id) && notesDeferred.get(id)!!.isActive){
        return notesDeferred.get(id)!!.await()
    } else {
        val newRequest = GlobalScope.async {
            remoteSource.getNotes(id)
        }
        notesDeferred.put(id, newRequest)
        return newRequest.await()
    }
}

[wcaokaze]

I have tried something similar.
https://github.com/wcaokaze/EfficientCoroutines/blob/master/src/main/java/com/wcaokaze/efficient/coroutines/TaskMap.kt#L144-L168

Sorry, this is not readable code.

[wcaokaze]

But I don't know whether this is the best way. Could somebody please tell us if there is a better way?

[bsimmons]

Interesting solution. What do you use launch time for?

[wcaokaze]

It's for something like that the second async starts after the first async finished. In this case, the second async do the task as usual (not await the first task).

[bsimmons]

Ok, makes sense. I guess I'm using .isActive to do that.