Here is my full program:
import Html exposing (..)
import Http
import Table exposing (defaultCustomizations)
import Json.Decode as Json exposing (field)
import Task
main =
Html.program
{ init = init
, update = update
, view = view
, subscriptions = \_ -> Sub.none
}
-- MODEL
type alias Show =
{ date : String
, format : String
, city : String
}
type alias Shows = List Show
type alias Model =
{ shows : Maybe Shows
, tableState : Table.State
}
init : ( Model, Cmd Msg )
init =
( { shows = Nothing
, tableState = Table.initialSort "Date"
}
, triggerReadingFromJson
)
-- UPDATE
type Msg
= SetTableState Table.State
| FetchSucceed (Maybe Shows)
| FetchFail Http.Error
update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
case msg of
SetTableState newState ->
( { model | tableState = newState }
, Cmd.none
)
FetchSucceed shows ->
( {model | shows = shows}
, Cmd.none
)
FetchFail _ ->
(model, Cmd.none)
-- VIEW
view : Model -> Html Msg
view { shows, tableState } =
div [] [ viewShows shows tableState ]
viewShows maybeShows tableState =
case maybeShows of
Nothing ->
text "No shows to display"
Just shows ->
Table.view config tableState shows
-- TABLE CONFIGURATION
config : Table.Config Show Msg
config =
Table.customConfig
{ toId = .date
, toMsg = SetTableState
, columns =
[ Table.stringColumn "Date" .date
, Table.stringColumn "Format" .format
, Table.stringColumn "City" .city
]
, customizations =
defaultCustomizations
}
-- HTTP
triggerReadingFromJson =
Http.toTask (Http.get "shows.json" decoderColl)
|> Http.send handleRequest
decoder : Json.Decoder Show
decoder =
Json.map3 Show
(field "date" Json.string)
(field "format" Json.string)
(field "city" Json.string)
decoderColl : Json.Decoder Shows
decoderColl =
Json.map identity
(field "shows" (Json.list decoder))
handleRequest result =
case result of
Ok val ->
FetchSucceed val
Err err ->
FetchFail err
On Wednesday, November 16, 2016 at 9:19:46 PM UTC+1, Peter Damoc wrote:
>
> The JSON failures are encapsulated in your Maybe, it should not pose any
> problem. It is defensive programming and it is just fine.
>
> You need to provide a full function, ideally complete with signatures, in
> order for me to try to understand why do you get that specific compiler
> error.
>
> What I provided has only two lines and should have worked (in theory).
> If you have altered it in a way that somehow reintroduces Tasks back, I
> need to see some code in order to try to figure out what's going on there.
>
>
>
>
>
>
> On Wed, Nov 16, 2016 at 10:07 PM, Tim Bezhashvyly <[email protected]
> <javascript:>> wrote:
>
>> This gives me
>>
>> (|>) is expecting the right side to be a: Task.Task Http.Error MyType ->
>>> a But the right side is: Http.Request (Maybe MyType) -> Cmd Msg
>>
>>
>> but maybe this is an artefact of old 0.17 architecture where I was too
>> defensive for the case if reading JSON fails.
>>
>> Sorry for trowing just an exception message but I'm really not sure how
>> to proceed here. :(
>>
>> And thank you for all your support so far.
>>
>> On Wednesday, November 16, 2016 at 8:25:23 PM UTC+1, Peter Damoc wrote:
>>
>>>
>>> On Wed, Nov 16, 2016 at 8:19 PM, Tim Bezhashvyly <[email protected]>
>>> wrote:
>>>
>>>> You mean something like:
>>>>
>>>> triggerReadingFromJson =
>>>> Http.toTask (Http.get "my.json" decoder)
>>>> |> Task.andThen (\result -> Task.succeed result)
>>>> |> Task.onError (\error -> Task.fail error)
>>>>
>>>> Task.andThen is used when you need to chain multiple requests like
>>> asking for some info from one endpoint and using the information received
>>> to make another call to a different endpoint based on the received info and
>>> encapsulate that into one, single, request so you get only one message.
>>>
>>> For what it looks like you try to accomplish, you just need to create
>>> the Request and use Http.send to convert it into a Cmd (the command that
>>> sends the request to the server)
>>>
>>> triggerReadingFromJson =
>>> Http.get myJsonUrl decoder
>>> |> Http.send (Result.Extra.unpack FailMessage SuccessMessage)
>>>
>>> I've used the helper suggested by Janis so you need to
>>> install elm-community/result-extra and add it to your dependencies. :)
>>>
>>>
>>>
>>>
>>>
>>>> But in this case the result is "Task.Task Http.Error MyType". What can
>>>> I do with it? I need somehow cast it to either MyType or Cmd, right?
>>>>
>>>>
>>>> On Wednesday, November 16, 2016 at 3:23:13 PM UTC+1, Peter Damoc wrote:
>>>>
>>>>> On Wed, Nov 16, 2016 at 4:05 PM, Tim Bezhashvyly <[email protected]
>>>>> > wrote:
>>>>>
>>>>>> Chained to Task.andThen and Task.onError? And what those tow must
>>>>>> return? I assume commands as they can't change model directly, right?
>>>>>>
>>>>>
>>>>> Chained with Task.andThen ;)
>>>>>
>>>>> As for the return type, I would return success and fail data and only
>>>>> at the last stage map it onto the message creators.
>>>>> The command is the equivalent of the Task in that it is a request for
>>>>> some side effects. It is not the result of the side-effect.
>>>>> The result of the side-effect is either some type decoded from some
>>>>> Json that is received (in the case of usual requests to Json APIs) or
>>>>> some
>>>>> kind of error type.
>>>>>
>>>>>
>>>>> So, in the case of Http, the final Cmd is a complex request that
>>>>> encapsulates a series of Http requests and is able to produce either a
>>>>> success msg or a fail msg.
>>>>> The data that end up in the messages gets there as a result of the
>>>>> execution of said Cmd.
>>>>> Which of the messages (success or failure) ends up in your update is
>>>>> also predicated on the execution of the Cmd.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>> On Wednesday, November 16, 2016 at 2:46:41 PM UTC+1, Peter Damoc
>>>>>> wrote:
>>>>>>>
>>>>>>> Sorry, old habits.
>>>>>>>
>>>>>>> The Http API became Cmd oriented. You don't need Task.attempt. Just
>>>>>>> use the regular Http.get and use the Cmds produced by it.
>>>>>>>
>>>>>>> If you need chaining, there is a `toTask` function that converts
>>>>>>> Requests to Tasks
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Wed, Nov 16, 2016 at 3:33 PM, Tim Bezhashvyly <
>>>>>>> [email protected]> wrote:
>>>>>>>
>>>>>>>> Thank. This makes lots of sense in regards of first argument.
>>>>>>>>
>>>>>>>> What about the second? In 0.17 it could be for example:
>>>>>>>>
>>>>>>>> (Http.get "my.json" decoderFunction)
>>>>>>>>
>>>>>>>> But not it produced an error:
>>>>>>>>
>>>>>>>> Function `attempt` is expecting the 2nd argument to be: Task.Task
>>>>>>>>> Http.Error (Maybe MyType) But it is: Http.Request MyType
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> On Wednesday, November 16, 2016 at 2:22:48 PM UTC+1, Peter Damoc
>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>> The old Task.perform was creating either a success message (if it
>>>>>>>>> succeeded) or a fail message (if it failed)
>>>>>>>>> The current Task.perform cannot fail. It is used for Tasks that
>>>>>>>>> are known to succeed like requesting the window size or requesting
>>>>>>>>> some
>>>>>>>>> random number.
>>>>>>>>>
>>>>>>>>> The Task.attempt takes a function that takes a result (results
>>>>>>>>> encapsulate both the success and the failure) and produces a message
>>>>>>>>> based
>>>>>>>>> on that result.
>>>>>>>>>
>>>>>>>>> You could define something like:
>>>>>>>>>
>>>>>>>>> handleRequest result =
>>>>>>>>> case result of
>>>>>>>>> Ok val ->
>>>>>>>>> SuccessMessage val
>>>>>>>>> Err err ->
>>>>>>>>> FailMessage err
>>>>>>>>>
>>>>>>>>> and use it like this:
>>>>>>>>>
>>>>>>>>> someHttpCmd = Task.attempt handleRequest someHttpRequestTask
>>>>>>>>>
>>>>>>>>> Alternatively, you could just have only one message that takes a
>>>>>>>>> Result and handle each case in that message's part of the update as
>>>>>>>>> demonstrated by the Http example:
>>>>>>>>> http://elm-lang.org/examples/http
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Wed, Nov 16, 2016 at 3:05 PM, Tim Bezhashvyly <
>>>>>>>>> [email protected]> wrote:
>>>>>>>>>
>>>>>>>>>> Sorry again if something obvious but Im not sure how now to make
>>>>>>>>>> async requests in 0.18.0.
>>>>>>>>>>
>>>>>>>>>> In 0.17.1 it was done with Task.perform where first parameter was
>>>>>>>>>> a success Msg, second - fail Msg and third is the task which
>>>>>>>>>> execution
>>>>>>>>>> result is then passed to first function.
>>>>>>>>>>
>>>>>>>>>> As far as I understand now Task.attempt must be used but
>>>>>>>>>> documentation is not quite comprehensive. Could someone please
>>>>>>>>>> advise?
>>>>>>>>>>
>>>>>>>>>> --
>>>>>>>>>> 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 [email protected].
>>>>>>>>>> For more options, visit https://groups.google.com/d/optout.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> --
>>>>>>>>> There is NO FATE, we are the creators.
>>>>>>>>> blog: http://damoc.ro/
>>>>>>>>>
>>>>>>>> --
>>>>>>>> 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 [email protected].
>>>>>>>> For more options, visit https://groups.google.com/d/optout.
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> There is NO FATE, we are the creators.
>>>>>>> blog: http://damoc.ro/
>>>>>>>
>>>>>> --
>>>>>> 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 [email protected].
>>>>>> For more options, visit https://groups.google.com/d/optout.
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> There is NO FATE, we are the creators.
>>>>> blog: http://damoc.ro/
>>>>>
>>>> --
>>>> 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 [email protected].
>>>> For more options, visit https://groups.google.com/d/optout.
>>>>
>>>
>>>
>>>
>>> --
>>> There is NO FATE, we are the creators.
>>> blog: http://damoc.ro/
>>>
>> --
>> 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 [email protected] <javascript:>.
>> For more options, visit https://groups.google.com/d/optout.
>>
>
>
>
> --
> There is NO FATE, we are the creators.
> blog: http://damoc.ro/
>
--
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 [email protected].
For more options, visit https://groups.google.com/d/optout.
