F# + recieve message DU instead of object.

[Neftedollar]

Hey!
I've found that the Receive method takes only a few types of Messages.
So I've tried to find where can I insert DU wrapper. I want to grains looks like

type MyGrain<MyMsg> =
  member x.Recieve ( msg: GrainMsg<MyMsg>) = 
    match msg with 
    | Msg(MyMsgCase1 x) -> none()
    | Time t -> t.GetType()|> printfn "%O"; none() // Orleankka.Tymire message 
    | OnActivate a -> a.GetType() //Activate type from https://github.com/OrleansContrib/Orleankka/blob/master/Source/Orleankka.Runtime/ActorGrainMessages.cs . also
    /// ..etc

but I didn't find any place in the F# packages where can I put middlware that will wrap objects with DU.
Can you help me with ideas for it?

[yevhen]

Just use nested match like here

P.S. Generic actor grains were deprecated since 2.x exactly due to this reason (we can’t have DU with system messages). DU are only for public interface, ie caller side type safety.

[Neftedollar]

Ok, maybe I should write something like

type GrainMessage<'t> = | Msg of 't | Timer of Timer  | ..
type TypedGrain<'t> () =
 inherit  ActorGrain() 
 abstract member this.TypedReceive ( msg: GrainMessage<'t>)
 override this.Receive (message) =
  match message with 
  | :? 't as msg -> this.TypedReceive(GrainMessage(msg))
  | :? Timer as msg -> this.TypedReceive(GrainMessage ( msg))
 .. etc

and then use it like ActorGrain but with TypedReceive method instead of Receive.
🤔

[Neftedollar]

I've created this

type ActorMsg<'t> =
    | Msg of 't
    | Timer of Orleankka.Timer
    | Reminder of Orleankka.Reminder
    | Activate of Orleankka.Activate
    | Deactivate of Orleankka.Deactivate

[<AbstractClass>]
type TypedActor<'a>() =
    inherit ActorGrain()
    abstract member ReceiveT: ActorMsg<'a> -> System.Threading.Tasks.Task<obj> 
    override this.Receive(msg:obj) = task {
      match msg with
      | :? 'a as m -> return! this.ReceiveT (Msg m)
      | :? Orleankka.Timer as t -> return! this.ReceiveT( Timer t)
      | :? Orleankka.Activate as a -> return! this.ReceiveT ( Activate a)
      | :? Orleankka.Deactivate as d -> return! this.ReceiveT( Deactivate d)
      | _ -> return unhandled() }

and use it like

type HelloGrain (loggerFactory:ILoggerFactory) =
  inherit TypedActor<HelloMessages>()
  let log = loggerFactory.CreateLogger(typeof<HelloGrain>)
  interface IHello
  override this.ReceiveT(msg) = task {
    match msg with
    | Msg(Hi)-> 
        log.LogInformation("Client asked to say Hi!")
        return some "Oh, hi!"
    | Msg(Hello s) ->
        log.LogInformation (sprintf "Client asked to say Hello to %s" s)
        return sprintf "Hello, %s" s |> some
    | Msg(Bue) -> 
        log.LogInformation ("Client wants to go")
        return none()
    | _ ->  return unhandled()
  }

and it's awesome!