在Gtk2HS中创建一个ComboBox小部件 [英] Create a ComboBox widget in Gtk2HS

问题描述

  void initGUI 
 window<  -  windowNew 
 
 ... 
 
 cb<  -  comboBoxNewText 
 comboBoxAppendText cb选项1
 comboBoxAppendText cb选项2
 comboBoxSetActive cb 0 
 boxPackStart hb cb PackNatural 0 
 
 ... 
  

但是出现此错误：

 无法将类型'[Char]'
与'text-1.2.2.0： Data.Text.Internal.Text'
预期类型：ComboBoxText 
实际类型：[Char] 
在'comboBoxAppendText'的第二个参数中，即
'Secuencial'
在'do'块的标记中：comboBoxAppendText cbSecuencial
在表达式中：
 do {void initGUI; 
窗口< -  windowNew; 
 set 
 window 
 [windowTitle：=A title，
 windowDefaultWidth：= 1024，....]; 
 vb < -  vBoxNew False 7; 
 ....} 
  

我只是遵循本教程（ http://www.muitovar.com/gtk2hs/chap4-2.html ）并阅读docs（ http://projects.haskell.org/gtk2hs/docs/gtk2hs-docs-0.9.12/Graphics-UI-Gtk-ModelView-ComboBox.html#v%3AcomboBoxInsertText ）

我该如何使它工作？

预先致谢。

解决方案

我建议在Hackage上使用文档。您链接的文档可能已过了十年。

从该文档，我们有

  type ComboBoxText = Text 
 comboBoxAppendText :: ComboBoxClass self =>自我 - > ComboBoxText  - > IO Int 
  

传递选项1作为 ComboBoxText 参数。在香草Haskell中，这是一个 String 而不是 Text - 如错误所述。您可以包 字符串，如

将合格的Data.Text导入为T 
 comboBoxAppendText cb（T.packOption 1）
  

或打开 OverloadedStrings 以自动完成字符串文字，as in：

  { - ＃LANGUAGE OverloadedStrings＃ - } 
 comboBoxAppendText cbOption 1
  code> 




I want to create a ComboBox widget with this code:

void initGUI
  window <- windowNew

  ...

  cb <- comboBoxNewText
  comboBoxAppendText cb "Option 1"
  comboBoxAppendText cb "Option 2"
  comboBoxSetActive cb 0
  boxPackStart hb cb PackNatural 0

  ...

But this error appears:

Couldn't match type ‘[Char]’
                   with ‘text-1.2.2.0:Data.Text.Internal.Text’
    Expected type: ComboBoxText
      Actual type: [Char]
    In the second argument of ‘comboBoxAppendText’, namely
      ‘"Secuencial"’
    In a stmt of a 'do' block: comboBoxAppendText cb "Secuencial"
    In the expression:
      do { void initGUI;
           window <- windowNew;
           set
             window
             [windowTitle := "A title",
              windowDefaultWidth := 1024, ....];
           vb <- vBoxNew False 7;
           .... }

I am just following this tutorial (http://www.muitovar.com/gtk2hs/chap4-2.html) and reading the docs (http://projects.haskell.org/gtk2hs/docs/gtk2hs-docs-0.9.12/Graphics-UI-Gtk-ModelView-ComboBox.html#v%3AcomboBoxInsertText)

How can i make it work?

Thanks in advance.

解决方案

I recommend using the documentation on Hackage. The documentation you linked is probably a decade stale by now.

From that documentation, we have

type ComboBoxText = Text
comboBoxAppendText :: ComboBoxClass self => self -> ComboBoxText -> IO Int

You are passing "Option 1" as the ComboBoxText argument. In vanilla Haskell, this is a String rather than a Text -- as the error says. You can either pack the String, as in

import qualified Data.Text as T
comboBoxAppendText cb (T.pack "Option 1")

or turn on OverloadedStrings to have this automatically done for String literals, as in:

{-# LANGUAGE OverloadedStrings #-}
comboBoxAppendText cb "Option 1"

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