How to pause for a measured time in Elm?

Question

I am attempting to create a simple web page using Elm which involves displaying an image for a measured amount of time, such as a second or a millisecond.

Is there a way to "pause" in Elm? Then I could display, pause, and then remove the image to achieve the effect.

I noticed the clock example but that appears to update every time the machine's clock triggers a new second, whereas I am looking for something that can pause to update a set time (such as a fraction of a second) after the starting time.

Answer 1

You can create a new Msg value which triggers url (of the image) changes. And create a subscription via Timer.every. You can add a flag in your model to indicate whether keep updating the image or not, if that's what you want.

Example:

subscriptions : Model -> Sub Msg
subscriptions model =
    if model.keepUpdating then
        Time.every (3 * second) (\x -> UpdateImage)
    else
        Sub.none


update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
    case msg of
        UpdateImage ->
            ( { model | image_url = "http://to_new_image/..." }, Cmd.none )

Answer 2

The elm-delay package provides a nice abstraction over timers. To create a Cmd RemoveImage that triggers in one second, you simply do after 1 second RemoveImage.