Enum

When dealing with enums there are a handful of functions which you end up writing again and again. This package creates them all for you in one go.

import Enum

type Fruit
    = Apple
    | Banana
    | Mango

fruit : Enum Fruit
fruit =
    Enum.create
        [ ( "Apple", Apple )
        , ( "Banana", Banana )
        , ( "Mango", Mango )
        ]

This gives you an Enum which is a record containing common helper functions:

type alias Enum a =
    { toString : a -> String
    , fromString : String -> Maybe a
    , encode : a -> Value
    , decoder : Decoder a
    , list : List ( String, a )
    }

Which you can then use like:

fruitListDecoder : Decoder (List Fruit)
fruitListDecoder = Decode.list fruit.decoder

encodeFruitList : List Fruit -> Value
encodeFruitList = Encode.list fruit.encode

There is also createInt for enums based on Int instead of String

Enum.fromIterator

One issue with enums is that when you add another variant, the compiler won't tell you if you forgot to update decoder etc. to include it. The same goes for Enum.create.

To solve this issue, this package includes an alternate way to create enums:

type Fruit
    = Apple
    | Banana
    | Mango

fruit : Enum Fruit
fruit =
    Enum.fromIterator
        (\a ->
            case a of
                Apple ->
                    ( "Banana", Banana )

                Banana ->
                    ( "Mango", Mango )

                Mango ->
                    ( "Apple", Apple )
        )
        Apple

The end result is exactly the same as with Enum.create, but the case..of helps ensure that you never forget to add a variant!

There's also the corresponding Enum.fromIntIterator.