Question

以下代码：

import Svg exposing (..)
import Window exposing (..)


init_size : Model msg -> Size
init_size _ =
    { width = 800, height = 600 }


type alias Model msg =
    { extra_size : Int
    , size : Size
    , child_elements : List (Svg msg)
    }

init_renderSpace : Model msg
init_renderSpace model =
    { extra_size = 40
    , size = init_size model
    , child_elements = []
    }

，产生一条我无法理解的奇怪错误消息。有谁知道我做错了什么？

这是错误消息：

-- TYPE MISMATCH ----------------------------------------------------- space.elm

The definition of `init_renderSpace` does not match its type annotation.

21| init_renderSpace : Model msg
22| init_renderSpace model =
23|>    { extra_size = 40
24|>    , size = init_size model
25|>    , child_elements = []
26|>    }

The type annotation for `init_renderSpace` says it is a:

    Model msg

But the definition (shown above) is a:

    Model msg
    -> { child_elements : List (Svg msg), extra_size : Int, size : Size }

Hint: It looks like a function needs 1 more argument.

Hint: The type annotation says there are NO arguments, but there is 1 argument
named in the definition. It is best practice for each argument in the type to
correspond to a named argument in the definition, so try that first!

基本上我尝试创建一个记录，该记录的参数基本上是svg节点列表。当我尝试使用空列表初始化模型时，我收到错误。

Answer 1

错误消息表示您init_renderSpace的类型定义为Model msg，但其实现为Model msg -> Model msg。换句话说，你是说init_renderSpace是一个模型，但它实际上是一个获取模型并返回模型的函数。

因为您没有在init_size中使用任何参数，我会从init_size和init_renderSpace删除参数：

init_size : Size
init_size =
    { width = 800, height = 600 }

init_renderSpace : Model msg
init_renderSpace =
    { extra_size = 40
    , size = init_size
    , child_elements = []
    }

在实例化记录中的Svg msg元素列表时出现奇怪的elm类型错误

1 个答案: