I did that if you look at link to marcosh's github I posted above. On Friday, August 12, 2016 at 1:50:12 PM UTC-5, OvermindDL1 wrote: > > Hmm, I'd be curious if you could whip up a full compileable example, say a > Multi-Counter project example we could paste into elm-try. Perhaps mark > things that are boilerplate and could be hoisted out to a parent library > too so we can ignore those? :-) > > > On Friday, August 12, 2016 at 12:15:20 PM UTC-6, Kasey Speakman wrote: >> >> Skimming through the code, it looks like batch commands will happen in >> order. The mentioned `mailbox.push` was from the Elm source code. >> >> Also, I fleshed out an example with both a clean separation and using >> event sourcing. I posted it with some commentary on marcosh's github >> <https://github.com/marcosh/marcosh.github.io/issues/1>. >> >> I like the terminology in this example much better than my previous >> examples, especially because `Action` was a previous concept in Elm. >> >> type Act = Increment | Decrement >> >> type Fact = Incremented Int | Decremented Int >> >> type Msg = Perform Act | Apply Fact >> >> perform : Act -> Model -> Cmd Msg >> >> apply : Fact -> Model -> Model >> >> update : Msg -> Model -> (Model, Cmd Msg) >> update msg model = >> case msg of >> Perform act -> >> (model, perform act model) >> >> Apply fact -> >> (apply fact model, Cmd.none) >> >> >> The Facts here are also idempotent >> <https://en.wikipedia.org/wiki/Idempotence> (no dependency on previous >> values). That's not as important in this example, but can as its extended. >> >> On Friday, August 12, 2016 at 9:15:23 AM UTC-5, OvermindDL1 wrote: >>> >>> Will your pushed command appear after or before a potentially pushed >>> 'other' command, say from an incoming port, or button click? That is the >>> part I am not sure about yet (not read enough Elm internals 'quite' yet). >>> >>> On Thursday, August 11, 2016 at 6:31:06 PM UTC-6, Kasey Speakman wrote: >>>> >>>> Checked the current implementation of Cmd.batch and it appears >>>> sequential (`mailbox.push`). Ordering guarantees are not documented so I >>>> suppose they shouldn't be depended on. But otherwise, the one I coded >>>> above >>>> that guarantees Act doesn't change the model and Evt doesn't have effects >>>> would work. >>>> >>>> On Thursday, August 11, 2016 at 6:33:39 PM UTC-5, Kasey Speakman wrote: >>>>> >>>>> Yes, that's why I said back to square one if Cmd.batch isn't ordered. >>>>> The only thing this is guaranteeing (and the only intended guarantee) is >>>>> that the messages which only update the model are separated from the ones >>>>> which cause effects. The ones which cause effects produce ones which >>>>> update >>>>> the model, same as always. >>>>> >>>>> It occurs to me that some of the benefit of event sourcing the UI >>>>> could be gained by adding features to the TTD, since it has the magic >>>>> which >>>>> ignores Cmds on replay. Some are already listed as ideas at >>>>> http://debug.elm-lang.org/. I'd still have to keep the messages in my >>>>> model and provide a way for the user to transmit them in a bug report. >>>>> But >>>>> if I could load them in the TTD, that would make repro a snap. >>>>> >>>>> On Thursday, August 11, 2016 at 5:22:05 PM UTC-5, OvermindDL1 wrote: >>>>>> >>>>>> Isn't `doSideEffects` basically just the current `update` function >>>>>> though? Except it is returning a list of changes (via message) to >>>>>> perform >>>>>> to a model instead of doing it in-place? What is this saving precisely? >>>>>> >>>>>> >>>>>> >>>>>> On Thursday, August 11, 2016 at 4:05:57 PM UTC-6, Kasey Speakman >>>>>> wrote: >>>>>>> >>>>>>> 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. >>>>>>>>>> >>>>>>>>>
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