how to use monadic forms?

Question

I am implementing a "contact me" form that will send an email when it is submitted. I needed this form to emit custom HTML, so I ended up using monadic forms. The problem is that I do not know how to use a monadic form.

the code is below. I have omitted the part that sends e-mail for brevity. the problem is that my form never validates correctly. the form result is never FormSuccess in my postContactR function.

It seems that I do not initialize the form correctly when I call runFormPost inside postContactR. I always pass Nothing instead of the actual ContactData to contactForm and I do not know how to construct my ContactData from the request. Is my understanding of the problem correct? I am trying to work with poorly documented features. :)

any help?

EDIT: what looks strange is that validation errors do show up in the form if I submit an invalid form, so the request data does get read at some point. what does not work is that when there are no errors I do not get redirected to RootR

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE TemplateHaskell #-}

module Handler.Contact where

import Control.Applicative ((<$>), (<*>))
import Data.Text (Text)
import Foundation
import Network.Mail.Mime

data ContactData = ContactData
                   { contactName    :: Text
                   , contactEmail   :: Text
                   , contactMessage :: Textarea
                   }
                 deriving Show

contactForm d = \html -> do
    (r1, v1) <- mreq textField "Your name:" (contactName <$> d)
    (r2, v2) <- mreq emailField "Your e-mail:" (contactEmail <$> d)
    (r3, v3) <- mreq textareaField "Message:" (contactMessage <$> d)
    let views = [v1, v2, v3]
    return (ContactData <$> r1 <*> r2 <*> r3, $(widgetFile "contact-form"))

getContactR :: Handler RepHtml
getContactR = do
    ((_, form), _) <- runFormPost (contactForm Nothing)
    defaultLayout $ do
        setTitle "contact"
        addWidget $(widgetFile "contact")

postContactR :: Handler RepHtml
postContactR = do
    ((r, form), _) <- runFormPost (contactForm Nothing)
    case r of
        FormSuccess d -> do
            sendEmail d
            setMessage "Message sent"
            redirect RedirectTemporary RootR
        _ -> getContactR

Answer 1

Are you including the html value in contact-form.hamlet? It's a nonce value. You'd get better debug information if you printed the value of r (in postContactR).

I have on my writing TODO list to add a monadic form example, it should be up soon.