Actually, I'd probably use a List instead of Maybe on the immediately
returned event(s).
doSideEffects : Act -> Model -> (List Evt, Cmd Evt)
doSideEffects act model =
case act of
UpdateCustomer customer ->
( [ CustomerUpdateRequested ]
, callServerWithCustomer customer
)
...
updateModel : Evt -> Model -> Model
... -- implementation as previous
update : Msg -> Model -> (Model, Cmd Msg)
update msg model =
case msg of
Action act ->
let
(events, command) = doSideEffects act model
in
(List.foldr updateModel model events, Cmd.map Evt command)
Event evt ->
(updateModel evt model, Cmd.none)
On Thursday, August 11, 2016 at 4:26:03 PM UTC-5, Kasey Speakman wrote:
>
> Yes, that was the goal. That way the UI state is utterly deterministic /
> reproducible in isolation of all outside services.
>
> That's a good point on the race conditions. I only use Cmd.batch because
> it's the facility that came to mind. (I'm still getting acquainted with
> Elm.) I don't know if Cmd.batch makes any ordering guarantee.
>
> If not we'd be more or less back to square one. Abuse `update` to do both
> things.
>
> doSideEffects: Act -> Model -> (Maybe Evt, Cmd Evt)
> doSideEffects act model =
> case act of
> UpdateCustomer customer ->
> (Just CustomerUpdateRequested, callServerWithCustomer customer)
>
> ...
>
> updateModel: Evt -> Model -> Model
> ... -- implementation as previous
>
> maybeUpdateModel: Maybe Evt -> Model -> Model
> maybeUpdateModel evtOpt model =
> case evtOpt of
> Nothing ->
> model
>
> Just evt ->
> updateModel evt model
>
> update : Msg -> Model -> (Model, Cmd Msg)
> update msg model =
> case msg of
> Action act ->
> let
> (eventNow, command) = doSideEffects act model
> in
> (maybeUpdateModel eventNow model, Cmd.map Evt command)
>
> Event evt ->
> (updateModel evt model, Cmd.none)
>
> So this should apply an event immediately if one is needed for the action.
> But it still keeps the model updating events separate.
>
> These immediate events would be seen by a userland event-store
> implementation (which is underneath updateModel), but I bet the TTD
> wouldn't see it since it doesn't come from Elm.
>
> On Thursday, August 11, 2016 at 3:43:36 PM UTC-5, OvermindDL1 wrote:
>>
>> So you really are wanting to hard device events into two different ones,
>> those that can *only* alter the model, and those that can *only* send
>> commands (which may call ones that alter the model). Unsure if it might
>> actually happen but might have to take into account possible race
>> conditions for if other messages appear before your other expected ones are
>> processed through? Easier to do that atomically all at once?
>>
>>
>> On Thursday, August 11, 2016 at 2:25:22 PM UTC-6, Kasey Speakman wrote:
>>>
>>> doSideEffects above would also have to map Cmd Evt to Cmd Msg.
>>>
>>
--
You received this message because you are subscribed to the Google Groups "Elm
Discuss" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to elm-discuss+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
