Can you use a string for record access in elm?

Question

If I have a string that looks like the name of a field in a record, can I use it to get the data somehow? Something like :

."name".toKey bill 
bill.(asSymbol "name")

-

song =
  { title = "foot", artist = "barf", number = "13" }

fieldsILike : List String
fieldsILike =
  [ "title", "artist" ]


val song key =
  .key song

foo = List.map (val song) fieldsILike --> should be ["foot", "barf"]

Answer 1

Not the way you want it but you can have a function that pattern matches on a string to access a part of a record. You need to be explicit about what it should do in case you give it something invalid.

import Html exposing (..) 

type alias Song = { artist : String, number : String, title : String }

song : Song
song =
  { title = "foot", artist = "barf", number = "13" }

fieldsILike : List String
fieldsILike =
  [ "title", "artist" ]


k2acc : String -> (Song -> String)
k2acc key = 
  case key of 
  "title" ->  .title
  "artist" -> .artist
  "number" -> .number
  _ ->  always ""

val : Song -> String -> String
val = flip k2acc 
-- `flip` was removed in elm 0.19, so you'll need to 
-- do something like the following going forward: 
-- val song field = (k2acc field) song   

foo = List.map (val song) fieldsILike

main = text <| toString foo