{-# OPTIONS_GHC -F -pgmFtrhsx #-}
import Happstack.Server
import HSP
import Happstack.Server.HSP.HTML
import Data.Monoid
{- We define a very simple data type here to use as our
instance for FromData -}
data Foo = Foo {bar :: Int,
baz :: Int}
deriving Show
{- Defining an instance of FromData is fundamentally simple. Primarily, you should use the helper function look
to grab the string associated with the named parameter you provide. From there, we use read to parse the string into an
int and return the final Foo. This isn't the safest construction, because the read could fail, but you can easily provide
yourself with more safety by using the MonadPlus instance of RqData and just calling mzero when an error occurs.-}
instance FromData Foo where
fromData = do
x <- read `fmap` look "bar"
y <- read `fmap` look "baz"
return $ Foo x y
main :: IO ()
main = simpleHTTP nullConf{port=8080} $ (dir "getHandler" handler) `mappend` (dir "postHandler" handler) `mappend` home
{- Please note that we actually use the same handler for both GET & POST requests.
This is an advantage of using FromData.
-}
handler :: ServerPartT IO Response
handler = do
mfoo <- getData
case mfoo of
Nothing -> webHSP $ didn'twork
Just foo -> webHSP $ displayFoo foo
displayFoo :: Foo -> HSP XML
displayFoo f =
This is a Foo