引入参数后编译 yesod 路由时遇到问题

Question

我是运行修改的例子 http://www.yesodweb.com/book/blog-example-advanced

以前没有使用 DBEntitySchemaId 类型的参数 id。自从介绍它，我得到

Handler/Entity.hs:146:34:
    Couldn't match type ‘DBEntitySchemaId -> Route App’
                  with ‘Route (HandlerSite (WidgetT App IO))’
    Expected type: WidgetT
                    App IO ((DBEntitySchemaId -> Route App) -> [(Text, Text)] -> Text)
     Actual type: WidgetT
                    App
                    IO
                    (Route (HandlerSite (WidgetT App IO)) -> [(Text, Text)] -> Text)
   In the first argument of ‘(>>=)’, namely ‘getUrlRenderParams’
   In a stmt of a 'do' block:
     (getUrlRenderParams
      >>=
        (\ urender_akdM
           -> (asWidgetT GHC.Base.. toWidget)
                (toHtml (\ u_akdN -> urender_akdM u_akdN [] EntityR))))

指的是使用defaultLayout的那一行。相关代码为：

getEntityR :: DBEntitySchemaId -> Handler Html
getEntityR id = do
  oldEntities <- runDB $ selectList [DBEntityDbentitySchemaId ==. id] []
  fields <- runDB $ selectList [DBFieldDbentitySchemaId ==. id, DBFieldFieldTypeId ==. (toSqlKey 1)] []
  mauthId <- maybeAuthId
  ((res, widget), enctype) <- runFormPost (form fields)
  case (mauthId,res) of
    (Just userId, FormSuccess (attributeValues)) -> do
      setMessageI $ MsgSubmittedKarma
      let entity = DBEntity "Test" id
      entId <- runDB $ insert entity
      let fieldsNVals = zip fields attributeValues
      let einfuegen field attributeValue = case (field, attributeValue) of
                                      ((Entity fldId _), (FormSuccess val)) -> do
                                         a <- runDB $ insert (Attribute {attributeEntityId = entId, attributeDbfieldId = fldId, attributeStringValue =  val})
                                         return (Just a)
                                      _ -> return Nothing
      _ <- forM fieldsNVals (\(field, attributeValue) -> einfuegen field attributeValue)

      redirect $ (EntityR id)
    _ -> do        
      --render <- getUrlRenderParams
      --return $ renderHtml $ [hamlet|
      defaultLayout [whamlet|
          $if null oldEntities
              <p>There are no entities
          $else
              <ul>
                  $forall Entity entityId entity  <- oldEntities
                      <li>
                          <p>#{dBEntityName entity}
          $if mauthId == Nothing
              <form method=post action=@{EntityR} enctype=#{enctype}>
                  <input type=submit value=_{MsgPleaseLogin}>
          $else
              <form method=post action=@{EntityR} enctype=#{enctype}>
                  ^{widget}
                  <input type=submit>
      |]

我已经尝试过将 whamlet 更改为 hamlet 和从这里添加一些代码行（注释掉）

Trying to send an email in yesod using hamlet

和改变

[whamlet|

到

[whamlet|@{getEntityR}/#{id}|

和

[whamlet||@?{urlParams id}|

以及受

启发的一些变体

Render url with query parameters https://groups.google.com/forum/#!topic/yesodweb/q1gtkOgM32I

我假设只需要做一个小的修改。不过我对whamlet/hamlet的理解不是太好。所以我发布这个以防这是一个微不足道的问题。我完全明白我需要做更多的工作，我只是无法用谷歌搜索我的问题。所以请多多包涵。

Answer 1

修改路由后忘记将新添加的参数传递给 @{EntityR} 插值，如下所示：@{EntityR param}.

引入参数后编译 yesod 路由时遇到问题

Having trouble compiling yesod route after introducing a parameter

haskell

yesod

hamlet