Text Templates in Elm

Elm offers built-in support for creating dynamic content or showing customized output to the user with the Html module. This module provides functions for creating HTML elements and attributes.

import Html exposing (..)
import Html.Attributes exposing (..)

main =
    div []
        [ textTemplate "some text"
        , textTemplate 5
        , textTemplate ["Elm", "Haskell", "PureScript", "F#"]
        , structTemplate { name = "Jane Doe" }
        , mapTemplate (Dict.fromList [("Name", "Mickey Mouse")])
        , conditionalTemplate "not empty"
        , conditionalTemplate ""
        , rangeTemplate ["Elm", "Haskell", "PureScript", "F#"]
        ]

textTemplate value =
    p [] [ text ("Value: " ++ Debug.toString value) ]

structTemplate record =
    p [] [ text ("Name: " ++ record.name) ]

mapTemplate dict =
    p [] [ text ("Name: " ++ Maybe.withDefault "" (Dict.get "Name" dict)) ]

conditionalTemplate str =
    p [] 
        [ text 
            (if String.isEmpty str then
                "no"
             else
                "yes"
            )
        ]

rangeTemplate list =
    p [] 
        [ text "Range: "
        , span [] (List.map (\item -> text (item ++ " ")) list)
        ]

In Elm, we don’t have a direct equivalent to Go’s text templates. Instead, we use functions to generate HTML. The Html module provides a way to create dynamic content.

We create separate functions for each type of template:

1. textTemplate takes a value and displays it.
2. structTemplate takes a record (Elm’s equivalent of a struct) and displays a field.
3. mapTemplate takes a dictionary and displays a value by key.
4. conditionalTemplate demonstrates conditional rendering.
5. rangeTemplate shows how to iterate over a list.

In Elm, we don’t have a separate template parsing step. Instead, we define our “templates” as functions that return HTML elements. The main function combines all these templates into a single view.

To run this Elm program, you would typically compile it to JavaScript and run it in a web browser. The output would be displayed as HTML elements on the web page.

Elm’s approach to templates is more type-safe and integrated with the language compared to Go’s string-based templates. While it might require more code for simple cases, it provides stronger guarantees and better integration with the rest of your Elm application.