Nettopologysuite

[kofhoang]

Hello! How would one accomplish this using Codecs?

type Geometry =
    { Geometry: NetTopologySuite.Geometries.Geometry }

    static member ToJson(x: Geometry) =
        let factory =
            NetTopologySuite.NtsGeometryServices.Instance.CreateGeometryFactory(x.Geometry.SRID)

        let options = JsonSerializerOptions()
        options.Converters.Add(NetTopologySuite.IO.Converters.GeoJsonConverterFactory(factory))

        jobj
            [ "srid" .= x.Geometry.SRID
              "geometry"
              .= Fleece.SystemTextJson.Extensions.Encoding(JsonSerializer.SerializeToElement(x.Geometry, options)) ]

    static member OfJson(json) =
        match json with
        | JObject o ->
            monad {
                let! (geoJson: JsonObject) = o .@ "geometry"
                let! (srid: int) = o .@ "srid"

                let factory =
                    NetTopologySuite.NtsGeometryServices.Instance.CreateGeometryFactory(srid)

                let options = JsonSerializerOptions()
                options.Converters.Add(NetTopologySuite.IO.Converters.GeoJsonConverterFactory(factory))

                return
                    { Geometry =
                        JsonSerializer.Deserialize<NetTopologySuite.Geometries.Geometry>(
                            geoJson |> Operators.toJsonValue,
                            options
                        ) }
            }
        | x -> Decode.Fail.objExpected x

[gusty]

@kofhoang codecs make sense when you can compose them, for instance types composed of other types which have codecs available.

In this case a pair of serializer/deserializer seem to be well "custom-made", of course you can always create a codec from a pair of functions but what's the point here?

Unless, you have other types composed with this one, in which case they could benefit of having a codec available.

[kofhoang]

@gusty Thank you, I seewhat you mean! What I am really trying to accomplish is to define serialization/deserialization for Nettopologysuite.Geometries.Geometry, which is a type I don't "own" and require options being passed like in the snippet. From what I understand, static members from type extensions are not taken into account by fleece, so the solution here would seem to be to define codecs, but I can't quite get the codec solution to work here. The solution above works, but not having to wrap the types would be preferable. Also, it seems a bit hacky to me :-)

[gusty]

I see, if the problem is not owning the original types source, read this section from the readme about combinators.

The example there is with codecs (notice the use of the <-> operator to create a codec) but in theory you should be able to use combinators for encoders and decoders as well.

If you feel the doc can be improved, let us know or just start a PR.

[kofhoang]

Great, that solved it! Many thanks. :-) It still looks a bit hacky like above, but at least now I was able to define a codec