Elm中不正确的View Functon返回类型 [英] Incorrect View Functon Return Type in elm

问题描述

我正在制作一个程序，将屏幕上的渲染文本更改为用户在文本框中输入的内容。我认为我的Elm体系结构模型和更新部分正确无误，但我真的不理解视图部分。

I am making a program that changes the rendered text on the screen to be whatever the user inputs in a text box. I think I have the model and the update part of the elm architecture correct, but I really don't understand the view portion.

我只是在把头包裹在方括号视图功能上时遇到麻烦。

I'm just having trouble wrapping my head around the square bracket view functions.

无论如何，我遇到此错误。

Anyway, I am getting this error.

此 div 调用产生：

Html #(Model -> Model)#

但是类型注释在视图上说应该是：

But the type annotation on view says it should be:

Html #Msg#Elm

但是我不确定如何更改视图函数以返回Html Msg，我有点困惑和一个字符串之间的区别。

But I am not sure how to change my view function to return Html Msg and I am kinda confused between the difference between that and a string.

谢谢大家！

这是我的代码...

module Main exposing (..)

import Browser
import Html exposing (Html, div, text, input, Attribute)
import Html.Attributes exposing (..)
import Html.Events exposing (onInput)

main =
  Browser.sandbox { init = init, update = update, view = view }

type alias Model = String

init : Model
init = "Hello, World!"

type alias Msg = String

update : Msg -> Model -> Model
update msg model =
  msg

view : Model -> Html Msg
view model =
  div []
    [ input [ placeholder "Input new string", value model, onInput update ] []
    , div [] [ text model ]
    ]

推荐答案

您正在通过 update 作为onInput的参数。您可能打算向其传递Msg，然后运行时将其传递给更新函数。

You're passing the update function as an argument to onInput. Your probably meant to pass it a Msg, which the runtime will then pass to the update function.

由于您的Msg类型是String的别名，因此可以使用 onInput身份

Since your Msg type is an alias for String, you can use onInput identity

这篇关于Elm中不正确的View Functon返回类型的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！