Elm

Question

这里是 Elm 新手。

当我用以下

替换下面 Mpower 模块中的 CustomerSelect 元素时

customers = ["Select Customer","Customer 1","Customer 2","Customer 3"]
customerSelect =
  select [ ]
    [ List.map customerItem customers
    ]

我得到一个 Elm 编译器 "Type Mismatch" 错误：

Function select is expecting the 2nd argument to be:
List VirtualDom.Node
But it is:
List (List Html)

这是从哪里来的？

module Mpower where

import Html exposing (..)
import List exposing (..)

customerItem custname =
  option [ ] [ text custname ]

customerSelect =
  select [ ]
    [
    customerItem "Select Customer",
    customerItem "Customer 1",
    customerItem "Customer 2",
    customerItem "Customer 3"
    ]

view =
  div []
    [ customerSelect
    ]

main =
  view

Answer 1

List.map 已经是 returns 一个列表，但是你仍然把它放在方括号中，所以它被包裹在另一个列表中。改为将其括在括号中：

customers = ["Select Customer","Customer 1","Customer 2","Customer 3"]
customerSelect =
  select [ ]
    (List.map customerItem customers)

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