decodeJson.elm

module Test where

import Text (asText)
import Array (Array, get)
import Json.Decode (..)
import Maybe (..)

type alias Foo =
  { foo : String
  , bar : Bar
  }

type alias Bar =
  { titi : String
  , toto : Maybe String
  , tutu : Int
  }

fooTest : String
fooTest =
  """
  [
    {
      "foo": "abcd",
      "bar": {
        "titi": "efgh",
        "tutu": 42
      }
    },
    {
      "foo": "ijkl",
      "bar": {
        "titi": "mnop",
        "toto": "qrst",
        "tutu": 123
      }
    }
  ]
  """

decodeFoo : Decoder Foo
decodeFoo = object2 Foo
  ("foo" := string)
  ("bar" := decodeBar)

decodeBar : Decoder Bar
decodeBar = object3 Bar
  ("titi" := string)
  (maybe ("toto" := string))
  ("tutu" := int)

foos : Decoder (Array Foo)
foos = array decodeFoo

main =
  let
    r : Result String (Array Foo)
    r = decodeString foos fooTest
  in
    case r of
      Ok  v -> asText (get 0 v)
      Err e -> asText e