如何在Elm中编码和解码简单的自定义类型？

type alias Person =
    { name : String
    , age : Int
    }

import Json.Encode exposing (Value, object, string, int)

encodePerson : Person -> Value
encodePerson person =
    object
        [ ( "name", string person.name )
        , ( "age", int person.age )
        ]

import Json.Decode exposing (Decoder, field, string, int)

decodePerson : Decoder Person
decodePerson =
    field "name" string
        |> andThen
            (\name ->
                field "age" int
                    |> map (Person name)
            )

import Json.Encode as Encode
import Json.Decode as Decode

person : Person
person =
    { name = "Alice"
    , age = 25
    }

encodedPerson : String
encodedPerson =
    Encode.encode 4 (encodePerson person)

decodedPerson : Result String Person
decodedPerson =
    Decode.decodeString decodePerson encodedPerson