digestive-functors and listOf

[Neil]

I've been able to use digestive-functors with simple forms successfully in a snap application; however, I'm getting stuck when trying to handle a list of hidden inputs. There is something I'm not quite getting on how to use 'listOf'. Can anyone point me in the right direction? Thanks.

The rendered html from a previous page includes the following hidden fields:

<div id='messageForm.recipients' class='inputList'>
  <input type='hidden' name='messageForm.recipients.indices' value='0' />
  <input type='hidden' id='messageForm.recipients.-1.email' name='messageForm.recipients.-1.email' value />
  <input type='hidden' id='messageForm.recipients.0.email' name='messageForm.recipients.0.email' value='emai1l@email.com' /> 
  <input type='hidden' id='messageForm.recipients.1.email' name='messageForm.recipients.1.email' value='email2@email.com' /> 
</div>


The data types are:

data ConfirmMessage = ConfirmMessage {
  isoDate :: T.Text,
  subject :: T.Text,
  body    :: T.Text,
  action  :: T.Text,
  recipients :: [Recipient]
} deriving (Show) 

data Recipient = Recipient {
  email :: T.Text 
} deriving (Show)


The forms are:

messageForm :: (Monad m) => Form T.Text m ConfirmMessage
messageForm = ConfirmMessage
  <$> "isoDate"    .: stringRead "Missing ISOdate" Nothing
  <*> "subject"    .: stringRead "Subject required" Nothing
  <*> "body"       .: stringRead "Body required" Nothing
  <*> "action"     .: stringRead "Missing action" Nothing
  <*> "recipients" .: listOf recipientForm' Nothing

recipientForm' :: (Monad m) => Formlet T.Text m Recipient
recipientForm'= Recipient
  <$> "email"      .: stringRead "Missing email" Nothing

Error message:
    Couldn't match type `Text.Digestive.Form.Internal.FormTree
                           m0 v0 m0 Recipient'
                  with `Maybe Recipient -> Form T.Text m Recipient'
    Expected type: Formlet T.Text m Recipient
      Actual type: Text.Digestive.Form.Internal.FormTree
                     m0 v0 m0 Recipient
    Relevant bindings include
      recipientForm' :: Formlet T.Text m Recipient
        (bound at src/Handler/TradeNotifyConfirm.hs:224:1)
    In the expression:
      Recipient <$> "email" .: stringRead "Missing email" Nothing
    In an equation for `recipientForm'':
        recipientForm'
          = Recipient <$> "email" .: stringRead "Missing email" Nothing

Thanks in advance,
Neil