下面的示例定义了一个snaplet，用于将nicEditor绑定到textarea。以下问题不仅与下面的例子有关，而且可能与其他类似案例有关。
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{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE OverloadedStrings #-}
------------------------------------------------------------------------------
-- | This module defines nicEditor snaplet, just a short example to show,
-- how snaplets can be defined together with splices.
-- License: BSD3.
-- Here are hopefully easy instructions, how to use or try:
--
-- 1. Make a directory, we'll use "netry" below, go there.
-- Initialize a project, e.g. "snap init default".
-- 2. Copy this file to netry/src-directory as SnapNic.hs.
-- 3. Add "import SnapNic" to Site.hs and to Application.hs
-- 4. Add ", _niced :: Snaplet Nicsnap" to data App in Application.hs
--
-- 5. Add "n <- nestSnaplet "niced" niced nicsnapInit" to
-- app :: SnapletInit App App in Site.hs.
-- 6. Add "addNicEditSplices n" to the same function as in step 5.
-- 7. Change the return-line of the same function as in step 5:
-- "return $ App h s a n"
-- that is, add "n" into the end. We need this because of step 4.
--
-- 8. Make route, e.g. ", ("/netext", with auth handleNEtext)" to
-- routes-function in Site.hs
--
-- 9. And then add handler into Site.hs:
-- handleNEtext :: Handler App v ()
-- handleNEtext = method GET handleForm <|> method POST handleFormSubmit
-- where
-- handleForm = render "textedit"
-- handleFormSubmit = do
-- p <- getParam "ots"
-- writeText "Submitting text from textarea...\n"
-- writeText (T.pack (show p))
--
-- 10. Last, add the following 2 templates to "netry/snaplets/heist/templates".
-- (This could be made simpler, but this works as an example of apply-tag.)
-- textedit.tpl:
-- <apply template="base">
-- <apply template="_textedit" />
-- </apply>
-- _textedit.tpl:
-- <h2>Your nic editor</h2>
-- <form method="post" action="netext">
-- <neTA/>
-- <button name="ne" value="ne" type="Submit">Send text</button>
-- </form>
-- <neScript/>
--
-- 11. Compile everything "cabal install -fdevelopment". After that,
-- if everything compiled, "netry -p 8000", start your browser and go
-- to "localhost:8000/netext".
--
-- TODO! This could use the config-files at least for some parameters, and more
-- tags,please. Tags could use some attributes (for example, size parameters
-- could be given as attributes of tags)...
--
module SnapNic
( Nicsnap (..)
, nicsnapInit
, addNicEditSplices
) where
------------------------------------------------------------------------------
import Control.Lens (makeLenses, view, (^.))
import qualified Data.Text as T (Text, append, pack)
import Data.Maybe (fromJust, fromMaybe)
import Snap.Core (MonadSnap)
import Snap.Snaplet (Snaplet
, makeSnaplet
, snapletValue
, SnapletInit
, Initializer
)
import Snap.Snaplet.Heist (HasHeist, addSplices)
import qualified Text.XmlHtml as X (Node (Element, TextNode))
import qualified Heist.Interpreted as I (Splice)
------------------------------------------------------------------------------
-- | Nicsnap has fields that can be used to set some basic properties.
-- The editor can have a title and its size can be set. Javascript can be
-- local or remote.
data Nicsnap = Nicsnap
{ _nicsnap :: T.Text -- title
, _areaSize :: (Int,Int) -- rows, cols
, _areaRef :: T.Text -- how to apply nicEditors?
-- (This may not be sufficient in order to refer in some other way, TODO!)
, _localR :: Maybe T.Text -- local route to nicEdit.js
, _webR :: T.Text -- route to nicEdit's javascript source.
}
makeLenses ''Nicsnap -- makes webR and other lenses
------------------------------------------------------------------------------
-- | Configurations are given here. This could use config-files...
-- What other things to configure?
-- If you want to make a local copy of the nicEdit, then add a static route
-- to the "routes"-function.
nicsnapInit :: SnapletInit b Nicsnap
nicsnapInit = makeSnaplet "nicsnap" "NicEditor snaplet " Nothing $ do
let m = "Nic editor title"
aS = (20,80)::(Int,Int) -- rows, cols
aR = "nicEditors.allTextAreas" -- TODO! We need to be able to tell,
-- which textareas have editors in a page.
lR = Nothing
-- lR = Just "/nicEdit.js"
-- If localR is nothing, then webR is used with the following addr.
wR = "http://js.nicedit.com/nicEdit-latest.js"
return $ Nicsnap m aS aR lR wR
------------------------------------------------------------------------------
-- | Internal, this makes the script-tag.
-- Input could be e.g. txt = "/nicEdit.js"
srcElem :: T.Text -> X.Node
srcElem txt = X.Element "script"
[("src",txt),("type","text/javascript")] []
-- | Internal, this makes the script-tag. At the moment this changes all
-- textareas to niceditors, if the example input below is used. TODO!...
-- Input could be e.g. txt = "nicEditors.allTextAreas"
srcOnLoad :: T.Text -> X.Node
srcOnLoad txt = X.Element "script" [("type","text/javascript")]
[X.TextNode (T.append (T.append "bkLib.onDomLoaded(" txt) ");")]
-- | Internal, used to define "divs", where we give a label and size to
-- textarea. Also ids and names.
-- TODO! ids and names could be parameters.
divLabelTX :: T.Text -> T.Text -> T.Text -> X.Node
divLabelTX title r c = X.Element "div" [("class", "required")]
[ X.Element "label" [("for","ots")]
[X.TextNode title]
, X.Element "textarea"
[("id","ots"), ("name","ots"), ("cols",c), ("rows",r)]
[X.TextNode " "]
]
-- | Internal, this can be used in splice-definition.
-- TODO! ids and names could be parameters, too.
nicTextAreaAdd :: MonadSnap m => T.Text -> (Int,Int) -> I.Splice m
nicTextAreaAdd title (r,c) = return [divLabelTX
title
(T.pack . show $ r)
(T.pack . show $ c)]
-- | Add script-tags to web page with splice that tell, what javascript
-- library to use...
nicEditAdd :: MonadSnap m => T.Text -> T.Text -> I.Splice m
nicEditAdd src edElems = return (srcElem src : [srcOnLoad edElems])
------------------------------------------------------------------------------
-- | Get the route to the javascript library that is applied (either local
-- library or construct a link to a web address).
nicRoute :: Nicsnap -> T.Text
nicRoute ns = let mlR = ns ^. localR in fromMaybe (ns ^. webR) mlR
------------------------------------------------------------------------------
-- | neTextAreaTag and neScripTag are used in addSplices to define the tags
-- to be used in templates.
-- What other tags could be useful? Maybe a way to add a nicEditor directly
-- with one or more button bind to it ("send", "clear", etc). TODO!
neTextAreaTag = "neTA" :: T.Text
neScriptTag = "neScript" :: T.Text
-- | Make the tags to be used in templates. At the moment, only the above
-- tags are defined.
addNicEditSplices :: HasHeist b => Snaplet Nicsnap -> Initializer b v ()
addNicEditSplices n = let m = view snapletValue n in addSplices
[(neTextAreaTag, nicTextAreaAdd (m ^. nicsnap) (m ^. areaSize))
,(neScriptTag, nicEditAdd (nicRoute m) (m ^. areaRef) )
]
------------------------------------------------------------------------------
答案 0 :(得分：1)
我不是新手，所以我无法回答你的第一个问题，但我对其他一些问题有一些想法和答案。首先，如果你真的希望这是一个严肃的snaplet（无论是出于教学目的还是实际用途），你应该把它变成一个cabal项目。这将消除您的指示中的第2步。接下来，snaplet可以定义自己的路由。您可以通过调用addRoutes函数在初始值设定项中执行此操作。这将消除步骤8. Snaplet还可以提供自己的文件系统资源，这些资源将被复制到使用它的任何项目中。您可以使用此功能来消除步骤10，以及提供默认配置文件。有关如何执行此操作的详细信息，请查看snaplet教程末尾的filesystem data and automatic installation部分。
目前，snaplet-postgresql-simple可能是关于如何使用snaplet必须提供的大多数功能的最佳示例。如果你想让它成为一个非常强大的通用snaplet供其他人使用，那么你绝对应该包括解释和编译的拼接。我最近在snap包中添加了一些new functions，这使得编写通用snaplet更容易，这些snaplet可以在编译或解释的拼接模式下自动工作。那段代码还没有用，但我很快就会发布它。
我一直致力于another snaplet，它可以更全面地使用snaplet API的大部分功能。与snaplet-postgresql-simple不同，此snaplet定义了模板和拼接。它仍处于开发阶段，但已经展示了大部分功能。剩下的工作大部分只是润色和坚固。