WebCont

WebConts allow simple continuation based behavior in Happstack applications through the use of cookies and an IntMap on the server mapping cookie names to continuations. It is based on the paste http://gist.github.com/260052. For the arc challenge:

    arc = do
        name <- doform' frm
        display $ samelink "click here"
        display $ "you said" ++ name

A more complicated example, creating a User datatype with a different page for each field:

   data User = User {age:: Int, name::String, dead::Bool} deriving (Show)
   makeUser = liftM3 User age name dead >>= (display . show) where
       age = doform' $ label "Age: " *> frm
       name = doform' $ label "Name: " *> frm
       dead = doform' $ label "Dead?: " *> frm

To run the continuations in Happstack, use runStateless or runWithState, giving each continuation in a list as a parameter, depending on whether you want MACID support enabled:

   runStateless nullConf [arc, makeUser] []

Documentation

doform :: (Html -> r) -> ([String] -> Html -> r) -> ContForm a -> WebCont r a

Lift a form into the WebCont monad using a function

doform' :: ContForm a -> WebCont Html a

Lift a form into the WebCont monad without embellishment, displaying errors inline

runWithState :: (Methods a, Component a) => Conf -> Proxy a -> [WebCont Html ()] -> [ServerPartT IO Response] -> IO ()

Entry point for the continuation server: sets up continuation table, MACID state, and a chron job to add a checkpoint daily

runStateless :: Conf -> [WebCont Html ()] -> [ServerPartT IO Response] -> IO ()

Entry point for the continuation server: starts the server without MACID support

display :: HTML a => a -> WebCont Html ()

Display a page, ignoring the value

samelink :: HTML a => a -> HotLink

Links to the same page, leading to the next step in a continuation

button :: String -> a -> WebCont Html a

Button with an associated value

link :: HTML l => l -> a -> WebCont Html a

Link with an associated value

newtype WebCont r a

A WebCont is a function from Env to a value of a, displaying a response of r. Both r and a must be Html for runnable continuations.

Constructors

WebCont

Fields

runWeb :: Env -> Result r a

Instances

Monad (WebCont r)

Show (WebCont r a)

(Monoid r, Monoid a) => Monoid (WebCont r a)

Monoid a => Monoid (WebCont a a)

data Result r a

Constructors

Done a

Via r (WebCont r a)

Instances

(Show r, Show a) => Show (Result r a)

type ContForm a = XHtmlForm Identity a

class DefaultForm i where

Defines a normal form style to use for a given type

Methods

frm :: Form Html Identity i

Instances

DefaultForm Bool

DefaultForm Int

DefaultForm Integer

DefaultForm String

(DefaultForm a, DefaultForm b) => DefaultForm (a, b)

nullConf :: Conf

Default configuration contains no validator and the port is set to 8000