榆树将json发布到rails答案

【问题标题】：elm post json to rails榆树将json发布到rails
【发布时间】：2018-08-01 19:16:33
【问题描述】：

我探索 Elm 和 Rails Api 作为服务器。从 Rails 获取数据很容易，但如何 POST。

Rails score.json中有一个表scores：

[
  {
  id: 1,
  name: "Larry",
  score: 100
  }
]

在 Elm 我有解码/编码

scoreDecoder : Decoder Score
scoreDecoder =
Decode.map3 Score
    (field "id" Decode.int)
    (field "name" Decode.string)
    (field "score" Decode.int)


encodeScore : Model -> Encode.Value
encodeScore model =
    Encode.object
    [ ("name", Encode.string model.name)
    , ("score", Encode.int (sumMarkedPoints model.entries))
    ]

还有一个命令：

postScore : Model -> Cmd Msg
postScore model =
let
    url =
        "http://localhost:3000/scores"

    body =
        encodeScore model
            |> Http.jsonBody

    request =
        Http.post url body scoreDecoder
in
    Http.send NewScore request

我有按钮发送消息：ShareScore

update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
ShareScore ->
        ( model, postScore model )

我得到：发布您的分数时出错：BadStatus { status = { code = 400, message = "Bad Request" }, headers = Dict.fromList [("content-type","application/json; charset=UTF-8")], url = "http://localhost:3000/scores", body = "{\"status\":400,\"error\":\"Bad Request\",\"exception\":\"#\u003cActionController::ParameterMissing: 参数丢失或值为空：

需要一些帮助来“解码”那个..

def score_params
  params.require(:score).permit(:id, :name, :score)
end

【问题讨论】：

标签： ruby-on-rails json ruby-on-rails-5 elm

【解决方案1】：

看来，Rails 期望您的输入类似于：

{
  score: {  
    name: "Larry",
    score: 100
  }
}

但您只传递了{ name: "Larry", score: 100 }，因此缺少必需的score 键。

其中一个选项是将您的编码器增强为：

encodeScore : Model -> Encode.Value
encodeScore model =
    Encode.object
        [ ( "score"
          , Encode.object
                [ ( "name", Encode.string model.name )
                , ( "score", Encode.int (sumMarkedPoints model.entries) )
                ]
          )
        ]

【讨论】：

谢谢。我也改变了： [ ( "name", Encode.string model.name ) , ( "score", Encode.int (sumMarkedPoints model.entries) ) ] 现在 Rails 抱怨：Bad payload"localhost:3000/scores", body = "{ \"id\":null,\"name\":\"Mike\",\"score\":220}" }
好的，我做到了..它看起来像是一个名称冲突表 model.score&&item.score。重命名为点后..作品..感谢帮助

【解决方案2】：

避免名称冲突..

 encodeScore : Model -> Encode.Value
 encodeScore model =
    Encode.object
     [ ( "score"
      , Encode.object
            [ ( "name", Encode.string model.name )
            , ( "points", Encode.int (sumMarkedPoints 
                model.entries) )
            ]
      )
    ]

【讨论】：