Say I have a function doSomething : a -> Cmd b and another getArgument : Task x a. Can I combine them to get a single Cmd b? Classic example would be getting current time with Time.now and passing it to a function Time.Posix -> Cmd b. In my case I want to use timestamp in the name of a file downloa…

You could write a “Helper-message” that could look like this: type Msg = ... | GetTimeFor (Time.Posix -> Msg) | SaveToFile String Time.Posix update : Msg -> Model -> (Model, Cmd Msg) update msg model = case msg of ... GetTimeFor toMsg-> (model, Task.perform toMsg T…

Neat idea @opsvager, I had never considered a recursive Msg type like that before. :+1:

Note that there are drawbacks to storing functions in your Msg type (same problems also apply to the Model type) Implications of storing functions in model or msg type

Agreed - these kinds of tricks comes at a cost. Alternatively, you could make a specialized GetTimeForSaveFile-message, without the type-parameter. It feels “dumber”, but it’s probably the best approach :sunny:

A similar but slightly different approach init : () -> ( Model, Cmd Msg ) init _ = ( () , Time.now |> Task.map timeToCmd |> Task.perform RunCmd ) type Msg = RunCmd (Cmd Msg) | ... update : Msg -> Model -> ( Model, Cmd Msg ) update msg model = case msg of …

Someone can correct me if I’m wrong about this but I believe storing Cmd or Task in your Msg/Model has the same drawbacks as storing functions.

Composing a Task with a function that returns a Cmd

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ursi October 13, 2020, 6:50pm 8

I believe most likely it does. Cmd.none == Cmd.none does work but trying to compare commands in general will result in an error.

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Composing a Task with a function that returns a Cmd

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