Elm：从http响应中解码json并显示

我是Elm的新手，我发现很难从http响应中解码json。
我正在制作的应用程式正在呼叫Gravatar并收到个人资料。我想从响应中提取一些字段并放入记录中，该记录又显示在视图中。这是我的代码：

-- MODEL

type alias MentorRecord =
    { displayName : String
    , aboutMe : String
    , currentLocation : String
    , thumbnailUrl : String
    }

type alias Model =
    { newMentorEmail : String
    , newMentor : MentorRecord
    , mentors : List MentorRecord
    }

init : ( Model, Cmd Msg )
init =
    ( Model "" (MentorRecord "" "" "" "") [], Cmd.none )

-- UPDATE

type Msg
    = MentorEmail String
    | AddMentor
    | GravatarMentor (Result Http.Error MentorRecord)
    | RemoveMentor

update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
    case msg of
        MentorEmail newEmail ->
            ( { model | newMentorEmail = newEmail }, Cmd.none )
        AddMentor ->
            ( model, getGravatarMentor model.newMentorEmail )
        GravatarMentor (Ok addedMentor) ->
            ( Model "" addedMentor (addedMentor :: model.mentors)
            , Cmd.none
            )
        GravatarMentor (Err _) ->
            ( model, Cmd.none )
        RemoveMentor ->
            ( model, Cmd.none )

-- VIEW
view : Model -> Html Msg
view model =
    div []
        [ input [ placeholder "Email adress mentor", onInput MentorEmail ] []
        , button [ onClick AddMentor ] [ text "Add Mentor" ]
        , br [] []
        , img [ src (createIconUrl model.newMentorEmail) ] []
        , div [] [ text model.newMentor.displayName ]
        , div [] [ toHtmlImgList model.mentors ]
        ]

toHtmlImgList : List MentorRecord -> Html Msg
toHtmlImgList mentors =
    ul [] (List.map toLiImg mentors)

toLiImg : MentorRecord -> Html Msg
toLiImg mentor =
    li [] [ img [ src mentor.thumbnailUrl ] [] ]

-- HTTP

getGravatarMentor : String -> Cmd Msg
getGravatarMentor newMentorEmail =
    Http.send GravatarMentor
        (Http.get (createProfileUrl newMentorEmail) decodeGravatarResponse)

createProfileUrl : String -> String
createProfileUrl email =
    "https://en.gravatar.com/" ++ MD5.hex email ++ ".json"

createIconUrl : String -> String
createIconUrl email =
    "https://www.gravatar.com/avatar/" ++ MD5.hex email

decodeGravatarResponse : Decoder MentorRecord
decodeGravatarResponse =
    let
        mentorDecoder =
            Json.Decode.Pipeline.decode MentorRecord
                |> Json.Decode.Pipeline.required "displayName" string
                |> Json.Decode.Pipeline.required "aboutMe" string
                |> Json.Decode.Pipeline.required "currentLocation" string
                |> Json.Decode.Pipeline.required "thumbnailUrl" string
    in
        at [ "entry" ] mentorDecoder

如果填写了一个有效的电子邮件地址（即带有gravatar配置文件的电子邮件地址），则会看到该图标。但是此代码还应该做的是从另一个http响应中提取名称，位置，关于我的信息，thumbnailUrl，并将其放在列表中，然后在视图中显示。如果您单击“添加导师”，则不会发生这种情况

因此，我想解码部分不会很好，但是我不确定（也许是因为嵌套元素在列表中？）。

来自gravatar的响应如下所示（已删除条目中的某些字段）：

{ "entry": [
    {
    "preferredUsername": "bla",
    "thumbnailUrl": "https://secure.gravatar.com/avatar/hashinghere",
    "displayName": "anne",
    "aboutMe": "Something...",
    "currentLocation": "Somewhere",
    }
]}

Ellie应用程序中的代码：https : //ellie-app.com/n5dxHhvQPa1/1