Elm: populating a record with List values - recursion

Question

Trying to learn Elm, and it's pretty hard :)
What I'm trying to accomplish:
I have a model that's a record with a number of key value pairs. I want to populate those keys with values from a list of strings.
module Main exposing (..)
import List
import Html exposing (Html, program, div, text)
type alias Model =
{ one: String
, two: String
, three: String
}
fakeData: List String
fakeData = ["foo", "bar", "baz", "bad", "baf"]
populate: Model -> List String -> Model
populate model data =
case List.head data of
Just str ->
case model.one of
"" ->
let updatedModel =
{ model | one = str }
in
case List.tail data of
Just items ->
populate updatedModel items
Nothing ->
model
_ ->
case model.two of
"" ->
let updatedModel =
{ model | two = str }
in
case List.tail data of
Just items ->
populate updatedModel items
Nothing ->
model
_ ->
case model.three of
"" ->
let updatedModel =
{ model | three = str }
in
case List.tail data of
Just items ->
populate updatedModel items
Nothing ->
model
_ ->
model
Nothing ->
model
init: ( Model, Cmd Msg)
init =
( populate { one = "", two = "", three = "" } fakeData, Cmd.none )
type Msg =
NoOp
view: Model -> Html Msg
view model =
div []
[ text (toString model) ]
update: Msg -> Model -> ( Model, Cmd Msg )
update msg model =
case msg of
NoOp ->
( model, Cmd.none )
subscriptions: Model -> Sub Msg
subscriptions model =
Sub.none
main: Program Never Model Msg
main =
program
{ init = init
, view = view
, update = update
, subscriptions = subscriptions
}
This program prints out:
{ one = "foo", two = "bar", three = "baz" }
I guess I have a hard time figuring out how to make this code less repetitive and easier to reason about. What if I have 20 keys in the model that all need to be populated? The above code would get pretty insane.

Answer 1

You could use pattern matching on the list instead:
populate : Model -> List String -> Model
populate model data =
case data of
one :: two :: three :: _ ->
{ model | one = one, two = two, three = three }
_ ->
model