Question

我正在尝试执行以下操作：

   Submit ->
        ( model, runtime.tryRegister model Response )

其中Response定义为：

| Response (Result Http.Error JsonProfile)

但是，以下函数无法编译：

tryRegister : Form -> (Result Http.Error a -> msg) -> Cmd msg
tryRegister form msg =
    let
        registerUrl =
            "http://localhost:5000/register"

        body =
            encode form |> Http.jsonBody

        request =
            Http.post registerUrl body decoder
    in
        Http.send msg request

错误：

Http.send msg request

函数send的第二个参数导致不匹配。 - 功能 send期待第二个参数为：
Http.Request a
但它是：
Http.Request JsonProfile

这是解码器：

decoder : Decoder JsonProfile
decoder =
    Decode.map4 JsonProfile
        (field "Id" Decode.int)
        (field "FirstName" Decode.string)
        (field "LastName" Decode.string)
        (field "Email" Decode.string)

source code can be found on GitHub。

Answer 1

如果您试图保持tryRegister功能通用，因为您不希望它与JsonProfile绑定，那么您需要将解码器作为参数传递，而不是引用键入decoder的顶级函数JsonProfile。

tryRegister : Form -> Decoder a -> (Result Http.Error a -> msg) -> Cmd msg
tryRegister form decoder msg =
    let
        registerUrl =
            "http://localhost:5000/register"

        body =
            encode form |> Http.jsonBody

        request =
            Http.post registerUrl body decoder
    in
        Http.send msg request

然后您可以在此处传递顶级decoder函数：

Submit ->
    ( model, runtime.tryRegister model decoder Response )

将Msg案例值作为泛型传递给执行Http.Post的另一个函数？

1 个答案: