Elm JSON Decoding

sample.elm

-- So I'm decoding JSON with this pattern, but there has to be a better way

import Json.Decode as JD

type alias User =
  { id : Int
  , email : String
  , firstName : String
  , lastName : String
  }

-- specifically here: this map4 seems dumb. This function depends on the proper
-- ordering of the fields to match the record constructor above. There must be
-- a better way, right?

jsonDecoder : JD.Decoder User
jsonDecoder = JD.map4 User
  (JD.field "id" int)
  (JD.field "email" string)
  (JD.field "firstName" string)
  (JD.field "lastName", string)

Hey! I built this tool to output Elm decoders for JSON: https://elm.quicktype.io/

Here's an order-independent decoder that it built given your User type:

otherUser : Jdec.Decoder OtherUser
user =
    Jpipe.decode User
        |> Jpipe.required "email" Jdec.string
        |> Jpipe.required "firstName" Jdec.string
        |> Jpipe.required "id" Jdec.int
        |> Jpipe.required "lastName" Jdec.string

It uses NoRedInk/elm-decode-pipeline.