Channel Directions in Elm

In Elm, we don’t have the concept of channels as in some other languages. Instead, we use a more functional approach with the Elm Architecture, which includes a model, update function, and view. For this example, we’ll create a simple program that demonstrates message passing using the Elm Architecture.

import Browser
import Html exposing (Html, button, div, text)
import Html.Events exposing (onClick)

-- MODEL
type alias Model =
    { message : String }

init : Model
init =
    { message = "" }

-- UPDATE
type Msg
    = Ping
    | Pong

update : Msg -> Model -> Model
update msg model =
    case msg of
        Ping ->
            { model | message = "Ping" }

        Pong ->
            { model | message = "Pong" }

-- VIEW
view : Model -> Html Msg
view model =
    div []
        [ button [ onClick Ping ] [ text "Ping" ]
        , button [ onClick Pong ] [ text "Pong" ]
        , div [] [ text model.message ]
        ]

-- MAIN
main =
    Browser.sandbox
        { init = init
        , update = update
        , view = view
        }

In this Elm program, we’ve created a simple application that demonstrates message passing:

We define a Model that holds a message string.
We create two message types: Ping and Pong.
The update function handles these messages by updating the model’s message field.
In the view function, we create two buttons that send Ping and Pong messages when clicked, and display the current message.
The main function sets up the Elm Architecture with our init, update, and view functions.

This example doesn’t directly translate the channel concept, but it demonstrates how Elm handles message passing and state updates, which is conceptually similar to what the original Go code was doing with channels.

To run this Elm program:

Save the code in a file named Main.elm.
Use the Elm compiler to compile it to JavaScript:

$ elm make Main.elm --output=main.js

Create an HTML file that includes the generated JavaScript:

<!DOCTYPE html>
<html>
<head>
    <title>Elm Ping Pong</title>
</head>
<body>
    <div id="elm-app"></div>
    <script src="main.js"></script>
    <script>
        var app = Elm.Main.init({
            node: document.getElementById('elm-app')
        });
    </script>
</body>
</html>

Open the HTML file in a web browser to see the Elm application in action.

This example demonstrates how Elm handles message passing and state updates in a functional, reactive way, which is conceptually similar to channel-based communication in other languages.

Channel Synchronization in Elm

Select in Elm

Learn X By Example

Title here

Channel Directions in Elm