In F#, converting int option to Google.Protobuf Int32Value

Question

Is there a more efficient way to convert an integer option type to Google.Protobuf.FSharp.WellKnownTypes.Int32Value before serializing it across a network? The code below works but feels awkward:

let f (x:int option) : ValueOption<Google.Protobuf.FSharp.WellKnownTypes.Int32Value> = 
    let bb = match x with
        | None -> ValueNone
        | Some xx -> ValueSome xx
    let c = {Int32Value.empty() with Value = bb }
    match c.Value with
    |ValueNone -> ValueNone
    |ValueSome s ->ValueSome c

TIA

Answer 1

Could you double-check that your snippet actually works? I'm a bit confused by that, because you seem to be creating Int32Value with Value set to an optional value - rather than an int32 value - and that does not look right to me.

That said, I think the most elegant option is to first turn option into ValueOption and then transform the value inside from int to Int32Value.

I do not see a built-in conversion function, so you may need to define your own:

module ValueOption = 
  let ofOption = function Some v -> ValueSome v | None -> ValueNone

Given this (and assuming I correctly understand Int32Value), you should be able to write something like:

let f (x:int option) : ValueOption<Google.Protobuf.FSharp.WellKnownTypes.Int32Value> = 
  x 
  |> ValueOption.ofOption
  |> ValueOption.map (fun n -> { Int32Value.empty() with Value = n })

Or if you prefer function composition over pipes (I do not, but many do):

let f =
  ValueOption.ofOption >>
  ValueOption.map (fun n -> { Int32Value.empty() with Value = n })