https://github.com/toastal/select-prism

Use a Monocle Prism to handle <select> conflict between ADTs and Strings
https://github.com/toastal/select-prism

adt elm optics select sum-types union-types

Last synced: about 2 months ago
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Use a Monocle Prism to handle <select> conflict between ADTs and Strings

• Host: GitHub
• URL: https://github.com/toastal/select-prism
• Owner: toastal
• License: apache-2.0
• Created: 2017-01-14T00:55:26.000Z (almost 8 years ago)
• Default Branch: main
• Last Pushed: 2021-07-04T10:17:38.000Z (over 3 years ago)
• Last Synced: 2024-10-01T09:19:48.360Z (3 months ago)
• Topics: adt, elm, optics, select, sum-types, union-types
• Language: Elm
• Homepage: http://package.elm-lang.org/packages/toastal/select-prism/latest/Html-SelectPrism
• Size: 18.6 KB
• Stars: 6
• Watchers: 4
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# select-prism

A `` is basically the UI representation of a [union type](http://elm-lang.org/docs/syntax#union-types) or ADT.Using a `Prism` and it’s data structure for a data transformation that’s not quite isomorphic, we can use go from an ADT to a `String` and back like we’d prefer to do.

```elm

import Html exposing (..)

import Html.SelectPrism exposing (selectp)

view : Model -> Html Msg

view { selectedColor } =

    -- Right Here ↓

    selectp colorp ChangeColor selectedColor [] colorOptions

colorOptions : List ( String, Color )

colorOptions =

    [ ( "❤️  Red", Red )

    , ( "💙 Blue", Blue )

    , ( "💚 Green", Green )

    ]

type alias Model =

    { selectedColor : Color }

type Msg

    = ChangeColor (Result String Color)

type Color

    = Red

    | Blue

    | Green

{-| You the developer are responsible for this `Prism`s correctness

-}

colorp : Prism String Color

colorp =

    let

        colorFromString : String -> Maybe Color

        colorFromString s =

            case s of

                "red" ->

                    Just Red

                "green" ->

                    Just Green

                "blue" ->

                    Just Blue

                _ ->

                    Nothing

        colorToString : Color -> String

        colorToString c =

            case c of

                Red ->

                    "red"

                Green ->

                    "green"

                Blue ->

                    "blue"

    in

        -- Using `Prism` as a constructor

        Prism colorFromString colorToString

```

Do check out [the example](https://github.com/toastal/select-prism/blob/master/examples/HeartColors.elm) and/or read [my blog entry](https://toast.al/posts/2017-01-13-playing-with-prisms-for-the-not-so-isomorphic.html) which goes into more depth.

---

## Project & Community Notes

This project is regrettably available on [GitHub](https://github.com/toastal/select-prism). The Elm community has tied itself to the closed-source, Microsoft-owned code forge of GitHub for package registry and identity. This does not protect the privacy or freedom of its community members.

---

## License

This project is licensed under Apache License 2.0 - [LICENSE](./LICENSE) file for details.

## Funding

If you want to make a small contribution to the maintanence of this & other projects

- [Liberapay](https://liberapay.com/toastal/)

- [Bitcoin: `39nLVxrXPnD772dEqWFwfZZbfTv5BvV89y`](bitcoin://39nLVxrXPnD772dEqWFwfZZbfTv5BvV89y?message=Funding%20toastal%E2%80%99s%20Elm%20select-prism%20development

) (verified on [Keybase](https://keybase.io/toastal/sigchain#690220ca450a3e73ff800c3e059de111d9c1cd2fcdaf3d17578ad312093fff2c0f))

- [Zcash: `t1a9pD1D2SDTTd7dbc15KnKsyYXtGcjHuZZ`](zcash://t1a9pD1D2SDTTd7dbc15KnKsyYXtGcjHuZZ?message=Funding%20toastal%E2%80%99s%20Elm%20select-prism%20development) (verified on [Keybase](https://keybase.io/toastal/sigchain#65c0114a3c8ffb46e39e4d8b5ee0c06c9eb97a02c4f6c42a2b157ca83b8c47c70f))