"Yesod devel“在fromJust in devel.hs中失败

Question

当我运行"yesod devel“时，上面写着"devel.hs: Maybe.fromJust: Nothing”

yesod init # created a project bbbb
...
cabal install && yesod devel
...
Registering bbbb-0.0.0...
Starting development server...
Starting devel application
devel.hs: Maybe.fromJust: Nothing

而且web服务器没有监听端口(我不能在浏览器中打开站点)。

有人知道怎么解决这个问题吗？

我的环境：

• yesod-0.9.4.1
• The Glasgow Haskell编译系统，7.0.3版
• Mac 10.6.8

以下是"yesod init“创建的dist/devel.hs：

{-# LANGUAGE PackageImports #-}
import "bbbb" Application (withDevelAppPort)
import Data.Dynamic (fromDynamic)
import Network.Wai.Handler.Warp
    (runSettings, defaultSettings, settingsPort, settingsHost)
import Data.Maybe (fromJust)
import Control.Concurrent (forkIO)
import System.Directory (doesFileExist, removeFile)
import System.Exit (exitSuccess)
import Control.Concurrent (threadDelay)

main :: IO ()
main = do
  putStrLn "Starting devel application"
  wdap <- (return . fromJust . fromDynamic) withDevelAppPort
  forkIO . wdap $ \(port, app) -> runSettings defaultSettings
    { settingsPort = port
    , settingsHost = "0.0.0.0"
    } app
  loop

loop :: IO ()
loop = do
  threadDelay 100000
  e <- doesFileExist "dist/devel-terminate"
  if e then terminateDevel else loop

terminateDevel :: IO ()
terminateDevel = exitSuccess

我上传了bbbb目录中的所有文件，Application.hs是https://github.com/suztomo/LanguageStudy/blob/master/Haskell/Yesod/bbbb/Application.hs。

Answer 1

在黑暗的答案:检查你的阴谋文件，你正在使用yesod-默认0.5。