I am not sure what you mean by routing to an implementation "in a generic
way".
You can clean up your code a lot by merging your "Model" type with "Impl".
This is the more idiomatic way of writing in Elm:
type alias Model =
CreateInvoiceImpl CreateInvoice.Model
| SendTextImpl SendText.Model
update : Msg -> Model -> Model
update message model =
case message of
CreateInvoiceMsg msg ->
CreateInvoice.update msg data
SendTextMsg msg ->
SendText.update msg data
On Tue, Aug 23, 2016 at 9:58 AM, Larry Weya <larryw...@gmail.com> wrote:
> Thank you for the response, routing to the proper implementation in a
> generic way is my problem. The command implementation should receive the
> json value and take care of decoding it.
>
> I ended up implementing it using case expressions which is ok but means I
> need to update the module in a number of place anytime I add a new command.
> I've pushed the code here
> <https://github.com/larryweya/dynamic-elm-modules/blob/master/CommandImpl.elm>
> if anyone wants to have a look.
>
> The issue is with the module that manages the commands (CommandImpl.elm)
> and how to defined a "generic" type which would hold a different kind of
> message and model depending on the command's name
>
> On Tuesday, 23 August 2016 18:04:13 UTC+3, Nick H wrote:
>>
>> This sounds like exactly the use case for Json.Decode.andThen
>> <http://package.elm-lang.org/packages/elm-lang/core/4.0.5/Json-Decode#andThen>.
>> (See that documentation for an example)
>>
>> Your could have your main module decode the JSON "params" enough to
>> figure out which type of message you've received, then route it to the
>> proper implementation.
>>
>> On Mon, Aug 22, 2016 at 4:25 AM, Larry Weya <larr...@gmail.com> wrote:
>>
>>> I have a project where I would like to have different implementations
>>> depending on a provided value.
>>>
>>> I have what we are referring to as Commands and we are using elm provide
>>> a UI used to configure a command's parameters so e.g. we have 2 Commands, a
>>> CreateInvoice command and a SendText command. They are persisted in a
>>> database as JSON. To edit the command, I load up the JSON and depending on
>>> the command's name I'd like my Main module to use the commands
>>> init/view/update functions. The biggest issue is that CreateInvoice and
>>> SendText models have different types.
>>>
>>> Main.elm
>>>
>>> -- how do I define a model that can accomodate both types
>>>
>>> main =
>>> Html.programWithFlags{...}
>>>
>>> init : String -> Json.Encode.Value -> Model
>>> init (moduleName, params) =
>>> -- how to init a command based on the moduleName
>>>
>>>
>>> CreateInvoice.elm
>>>
>>> type alias Model = {amount : Int}
>>>
>>> init jsonValue =
>>> -- decode json value into model
>>>
>>> SendText.elm
>>>
>>> type alias Model = {message : String}
>>>
>>> init jsonValue =
>>> -- decode json value into model
>>>
>>>
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