The Elm Architecture

Elm Architecture link

The Elm Architecture is a pattern for architecting interactive programs, like webapps and games.

This architecture seems to emerge naturally in Elm. Rather than someone inventing it, early Elm programmers kept discovering the same basic patterns in their code. It was kind of spooky to see people ending up with well-architected code without planning ahead!

So The Elm Architecture is easy in Elm, but it is useful in any front-end project. In fact, projects like Redux have been inspired by The Elm Architecture, so you may have already seen derivatives of this pattern. Point is, even if you ultimately cannot use Elm at work yet, you will get a lot out of using Elm and internalizing this pattern.

Components of The Elm Architecture link

TEA revolves around three main concepts: Model, Update, and View. Together, these components create a unidirectional data flow that is easy to understand and debug.

Model link

The model represents the state of your application. It’s a data structure (like a record) that contains all the information needed to render your app.

  type alias Model =
    { message : String
    }
  

Update link

The update function is where you define how your application responds to different messages (or actions). It takes a message and the current model, and returns an updated model.

  type Msg = UpdateMessage String

update : Msg -> Model -> Model
update msg model =
    case msg of
        UpdateMessage newMessage ->
            { model | message = newMessage }
  

View link

The view function takes the current model and returns HTML. Elm uses a virtual DOM, which makes updating the view very efficient.

  view : Model -> Html Msg
view model =
    Html.text model.message
  

Simple Application Example link

Let’s put these concepts together in a simple Elm application. The application will display a message and update it when a button is clicked.

  module Main exposing (..)

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

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

initModel : Model
initModel =
    { message = "Hello, Elm!"
    }

-- UPDATE
type Msg = UpdateMessage

update : Msg -> Model -> Model
update msg model =
    case msg of
        UpdateMessage ->
            { model | message = "Button clicked!" }

-- VIEW
view : Model -> Html Msg
view model =
    div []
        [ text model.message
        , button [ onClick UpdateMessage ] [ text "Click me!" ]
        ]

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

In this program, clicking the button triggers an UpdateMessage, which updates the model’s message. The view then reflects this change.

Advanced Topics in TEA link

As you become more familiar with TEA, you can explore its advanced features, which include handling side effects, managing complex state, and integrating with JavaScript.

Handling Side Effects link

In Elm, side effects (like HTTP requests) are managed in a controlled way using commands (Cmd). The Elm Architecture handles these commands to perform side effects and then routes the results back to your application.

  type Msg = FetchData | ReceiveData String

update : Msg -> Model -> (Model, Cmd Msg)
update msg model =
    case msg of
        FetchData ->
            (model, fetchDataCmd)
        ReceiveData data ->
            ({ model | data = data }, Cmd.none)
  

Managing Complex State link

For more complex applications, you can split your model and update logic into smaller parts. This approach helps in managing state more effectively and keeps your codebase organized.

Integrating with JavaScript link

Elm allows you to integrate with JavaScript using ports. Ports enable communication between Elm and JavaScript, allowing you to leverage JavaScript libraries and functionality within your Elm application.

  port module Main exposing (..)

port alert : String -> Cmd msg

update : Msg -> Model -> (Model, Cmd Msg)
update msg model =
    case msg of
        AlertMessage ->
            (model, alert "This is an alert!")
  

Understanding and mastering The Elm Architecture will enable you to build robust, maintainable, and scalable web applications in Elm.

Learn How To Build AI Projects link

Now, if you are interested in upskilling in 2024 with AI development, check out this 6 AI advanced projects with Golang where you will learn about building with AI and getting the best knowledge there is currently. Here’s the link.