haskell - 使用 warp 时出现 "no instance for YesodDispatch"错误

Question

平安!我使用 Yesod 编写了以下程序:

main = warp 2060 $
  onStatic "home" (dispatchTo $ return $ h1 $ toHtml "Sheepfold")

但是当我运行它时，出现以下错误:

No instance for (YesodDispatch
                   (Control.Monad.Trans.Writer.Lazy.Writer LiteApp ()))
  arising from a use of `warp'
Possible fix:
  add an instance declaration for
  (YesodDispatch (Control.Monad.Trans.Writer.Lazy.Writer LiteApp ()))
In the expression: warp 2060
In the expression:
  warp 2060
  $ onStatic "home" (dispatchTo $ return $ h1 $ toHtml "Sheepfold")
In an equation for `main':
    main
      = warp 2060
        $ onStatic "home" (dispatchTo $ return $ h1 $ toHtml "Sheepfold")

有人能帮忙吗？

Answer 1

您需要调用 liteApp。参见 this example for a demonstration .