ELM: Encoding Custom Types to JSON. Decoding Custom Types from JSON.

dec_enc_json_custom.elm

type Custom = Custom String

type alias P =  { i : Int, s: String, c: Custom }
p = P 4 "mo" (Custom "jo")

import Json.Encode as E
import Json.Decode as D

enc : P -> E.Value
enc a = E.object [("c", E.string (case a.c of Custom str -> str)), ("i", E.int a.i), ("s", E.string a.s)]

j = enc p

json = E.encode  0 j

dec : D.Decoder P
dec = D.map3 P (D.field "i" D.int) (D.field "s" D.string) (D.field "c" D.string |> D.andThen (\str -> D.succeed (Custom str)))


D.decodeString dec json