在客户端/服务器编程中使用3penny-gui /响应 [英] using threepenny-gui/reactive in client/server programming

问题描述

我想弄清楚如何使用Haskell 以及它的< a href =http://hackage.haskell.org/package/threepenny-gui-0.4.2.0/docs/Reactive-Threepenny.html =nofollow> reactive 功能来编写程序，让
$ b

• 用户从列表框中选择一个项目


• 将选择内容发送到外部服务器
li>

• 从服务器获取结果列表


• 使用结果填充列表框


• 重复
>

看来我需要使用 Handler ， newEvent 和寄存器来完成上述操作。如果有人可以指向我现有的代码，这样做会很好。

我找到的最接近的是 GameThing.hs 在threepenny-gui samples 目录中（但它不使用 register ）。

UPDATE：

我在问是否应该使用 Handler ， newEvent 和 register ---，如果有的话，这些函数的一些说明或示例。

另外，要清楚的是，大图是：

 浏览器 - > threepenny-gui（在本地主机上） - >后端服务器（网络上的任何地方）
 < -  < -  
  

单词，我需要做一些IO（基于用户选择），然后显示该IO的结果。

更新：这里是我的解决方案（基于@Taldykin的回复） ： https://github.com/haroldcarr/rdf-triple-浏览器/ tree / master / haskell / src

解决方案

这是一段代码。

  { - ＃LANGUAGE LambdaCase＃ - } 
 import Graphics.UI.Threepenny作为UI 
 
 
 main :: IO（）
 main = do 
（evFillList，doFillList）<  -  newEvent 
 initialList<  -  valuesSupply& 
 behFillList<  -  stepper initialList evFillList 
 
 startGUI defaultConfig $ \win  - > do 
 list<  -  ul 
 sel<  -  listBox 
 behFillList 
（纯粹无）
（纯$ \it  - > UI.span＃set文本）
 
 getBody win＃+ [grid [[element list，element sel]]] 
 setFocus $ getElement sel 
 
 on selectionChange（getElement sel）$ \ case 
 Nothing  - > return（）
只是ix  - >做
项目<  -  currentValue behFillList 
让它=项目！ ix 
 liftIO $ valuesSupply it>> = doFillList 
 element list＃+ [li＃set html it] 
 setFocus $ getElement sel 
 
 
 valuesSupply :: String  - > IO [String] 
 valuesSupply x = return [x ++ show i | i<  -  [0..9]] 
  

I am trying to figure out how to use Haskell threepenny-gui with its reactive functionality to write a program that lets

• the user select an item from a listBox
• send the selection to an external server
• get back a list of results from the server
• populate the listBox with the results
• repeat

It seems I will need to use Handler, newEvent and register to do the above. If someone could point me to some existing code that does something like the above that would be great.

The closest I have found is GameThing.hs in the threepenny-gui samples directory (but it doesn't use register).

UPDATE:

I am asking whether I should be using Handler, newEvent and register --- and, if so, some clarification or example of those functions.

Also, to be clear, the big picture is:

browser  --> threepenny-gui (on localhost) --> backend server (anywhere on network)
         <--                               <--

In other words, I need to do some IO (based on user selection) then display the results of that IO.

UPDATE: here is my solution (based on @Taldykin's response): https://github.com/haroldcarr/rdf-triple-browser/tree/master/haskell/src

解决方案

Here is a piece of code. I will add description a bit later.

{-# LANGUAGE LambdaCase #-}
import Graphics.UI.Threepenny as UI


main :: IO ()
main = do
  (evFillList, doFillList) <- newEvent
  initialList <- valuesSupply ""
  behFillList <- stepper initialList evFillList

  startGUI defaultConfig $ \win -> do
    list <- ul
    sel <- listBox
        behFillList
        (pure Nothing)
        (pure $ \it -> UI.span # set text it)

    getBody win #+ [grid [[element list, element sel]]]
    setFocus $ getElement sel

    on selectionChange (getElement sel) $ \case
      Nothing -> return ()
      Just ix -> do
        items <- currentValue behFillList
        let it = items !! ix
        liftIO $ valuesSupply it >>= doFillList
        element list #+ [li # set html it]
        setFocus $ getElement sel


valuesSupply :: String -> IO [String]
valuesSupply x = return [x ++ show i | i <- [0..9]]

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