CODEWITHSUNDEEP
datetimeelm
Stanko
Stanko

Reputation: 4465

Initialize model with current date

I'm trying to initialize my model with the current date. I don't want to use a Native module. I'm trying to do it with Task and Effects. I'm stuck at my getCurrentTime method. What is the cleanest way?

import Time exposing ( Time )
import StartApp
import Task
import Effects exposing (Never)
import Html exposing ( Html )

app = 
  StartApp.start
    { init = init
    , view = view
    , update = update
    , inputs = []}

main = 
  app.html

port tasks : Signal (Task.Task Never ())
port tasks =
  app.tasks

type alias Model = 
    { clock : Time}

init : (Model, Effects.Effects Action)
init = ((Model  ), Effects.none)

type Action = ShowClock 

update : Action -> Model -> (Model, Effects.Effects Action)
update action model = 
  case action of
    ShowClock c -> 
      ({ model | clock = c}, Effects.none)

getCurrentTime : Effects.Effects Action
getCurrentTime =
  -- stuck here
  |> Task.map ShowClock
  |> Effects.task

view : Signal.Address Action -> Model -> Html
view address model =
  Signal.map Html.text model.clock

It would also be nice to convert the time to a string with "YYYY-MM-DD" format.

Upvotes: 4

Views: 631

Answers (2)

Max Dy
Max Dy

Reputation: 307

There is an ELM package available at http://package.elm-lang.org/packages/evancz/task-tutorial/1.0.3/TaskTutorial you can use to get the current time.

First you need to download it and update your elm-package.json file using the following command in a terminal or Windows command:

elm-package install evancz/task-tutorial 1.0.3

Then update your code :

getCurrentTime : Effects.Effects Action
getCurrentTime = Effects.task <| Task.map ShowClock ( TaskTutorial.getCurrentTime )

Finally, you just have to call getCurrentTime as an Effects Action and your model will be updated.

To convert your Time into a human readable date String you can use this little helper function:

 toHRDate : Time -> String -- to human readable date
 toHRDate t =
     let
       date = Date.fromTime t
       d = toString (Date.day date) -- day
       m = toString (Date.month date) -- month
       y = toString (Date.year date) -- year
       hrd = d ++ "-" ++ m ++ "-" ++ y
    in hrd

Upvotes: 2

grumpyjames
grumpyjames

Reputation: 366

If we simply want to pass an initial value at the beginning of your program, we can use a port:

So, we'd add this to the application that contains main:

port time : Float

...and then we have to add the following to our html to give our elm program the correct initial value.

var myapp = Elm.fullscreen(Elm.YourAppNameHere, 
                           {
                               time: Date.now()
                           });

The interop documentation on the elm language website covers this reasonably and has links to several other examples: http://elm-lang.org/guide/interop

Alternatively, you could try out foldp' from the Signal.Extra library, which exposes initial values a little more explicitly. http://package.elm-lang.org/packages/Apanatshka/elm-signal-extra/5.7.0

Upvotes: 1

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