榆树:解码Http.Error

Question

我想知道如何解码榆树中的Http.Error并将其数据存储在我的模型中.

我知道错误响应将返回此结构.

{
  error: "Some error message",
  ok: false
}

这是我的模型和我的Http请求

type alias Model =
  { url = String
  , result : String
  , errorMessage : String
  , error : Bool
  }

model : Model
model =
  { url = ""
  , result = ""
  , errorMessage = ""
  , error = False
  }

-- make the request

makeRequest : String -> Cmd Msg
makeRequest url =
  Task.perform FetchFail FetchSucceed (Http.get decodeTitle url)

-- decode the success response

decodeTitle : Json.Decoder String
decodeTitle =
  Json.at ["title"] Json.string

-- decode the error

decodeError =
  Json.object2 User
    ("error" := Json.string)
    ("ok" := Json.bool)

我希望我可以在FetchFail我的更新中处理这个问题.

type Msg
  = FetchTitle
  | FetchSucceed String
  | FetchFail Http.Error


update : Msg -> Model -> (Model, Cmd Msg)
update action model =
  case action of
    ...

    FetchFail err ->
      let
        error =
          decodeError error
      in
        ({ model | ok = error.ok, errorMessage = error.error}, Cmd.none)

任何帮助表示赞赏.

Answer 1

榆树0.17:

Http.Error类型是一种联合类型,如果有的话,它可以保存响应代码.

类型错误=超时| NetworkError | UnexpectedPayload字符串| BadResponse Int String

您可以case通过err变量来访问它.

FetchFail err ->
  case err of
    BadResponse code error ->
      -- handle error message
    _ ->
      -- other error

http://package.elm-lang.org/packages/evancz/elm-http/3.0.1/Http#Error

使用elm 0.18并转换到elm-lang/http时,错误类型已被修改:

type Error
    = BadUrl String
    | Timeout
    | NetworkError
    | BadStatus (Response String)
    | BadPayload String (Response String)