[Haskell-cafe] Happstack: moving the uploaded file

[Tom Ellis]

On Tue, Jun 03, 2014 at 12:31:14AM +0400, Nikita Karetnikov wrote:
> I’d like the code to look like ‘UploadFile.hs’, but it doesn’t work
> properly.  Could anyone explain why?

Yes, you can't receive the client's request containing the form data in the
reponse that sends out the form!

> tempFile :: ServerPart Response
> tempFile = do
>   (tmpFile, _, _) <- lookFile "file_upload"
>   liftIO $ renameFile tmpFile permFileLoc
>   file <- liftIO $ readFile permFileLoc
>   showFile file
> 
> permFile :: ServerPart Response
> permFile = do
>   file <- liftIO $ readFile permFileLoc
>   showFile file

Why not merge these with something like (unchecked!)

readFile :: ServerPart Response
readFile = do
  flip (<|>) (return ()) $ do
      (tmpFile, _, _) <- lookFile "file_upload"
      liftIO $ renameFile tmpFile permFileLoc
  file <- liftIO $ readFile permFileLoc
  showFile file

Tom