oh my gosh, so this is a bit of a rant. I just lis...

# random

[groostav]

oh my gosh, so this is a bit of a rant. I just listened to the talking kotlin episode on a GRPC target for kotlin. This reminded me of my (bad) GRPC project. I dug up that code

fun <M, R> sendAndAwaitResponse(func: KFunction2<M, StreamObserver<R>, Unit>): suspend (request: M) -> R = { request: M -> sendAndAwaitResponse(func, request) }

// sends a message, and converts the response observer to kotlin suspension (and exception) semantics
// assumes a unary call (that is, a call with one value given to the response observer)
suspend fun <M, R> sendAndAwaitResponse(func: KFunction2<M, StreamObserver<R>, Unit>, request: M): R {
    val source = RuntimeException("server replied with error on call to ${func.name} with $request")

    return suspendCoroutine<R> { continuation ->
        func(request, object: StreamObserver<R> {
            var result: ResponseState<R> = ResponseState.NoValue

            override fun onNext(value: R) {
                //...
            }
            override fun onError(thrown: Throwable) {
                //...
            }
            override fun onCompleted() {
                //...
                continuation.resumeWith(result)
            }
        })
    }
}

// "idiomatic" usage:
sendAndAwaitResponse(grpcService::someUnaryServiceMethod)(RequestDTO.newBuilder()....)

One of the things I was hailing kotlin for is that you dont often (ever?) end up with functions-returning-lambdas as is sometimes convention in Scala --typically to help the scala type inference engine. Well here I am doing exactly that

fun <M, R> sendAndAwaitResponse(func: KFunction2<M, StreamObserver<R>, Unit>): suspend (request: M) -> R = { request: M -> sendAndAwaitResponse(func, request) }

is doing.

tl;dr kotlin > scala; if you're using grpc try the new kotlin GRPC target. Suspend funs are good.

[groostav]

I suppose for the arrow guys this is pretty basic stuff

[groostav]

kotlin GRPC target --avoids a lot of nastyness

[groostav]

https://github.com/grpc/grpc-kotlin