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" .: text Nothing
The error message I am getting is:
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:191:1)
In the expression: Recipient <$> "email" .: text Nothing
In an equation for `recipientForm'':
recipientForm' = Recipient <$> "email" .: text Nothing
Okay disclaimer: I have never used digestive-functors
, but here is how I approach this kind of problem:
1) Your error message says Expected type: Formlet T.Text m Recipient
and Actual type: Text.Digestive.Form.Internal.FormTree m0 v0 m0 Recipient
2) Look at the documentation and see that:
type Formlet v m a = Maybe a -> Form v m a
type Form v m a = FormTree m v m a
so we expand the expected from above to get:
Formlet T.Text m Recipient
-- v ~ T.Text, a ~ Recipient
Maybe Recipient -> Form T.Text m Recipient
--
Maybe Recipient -> FormTree m T.Text m Recipient
now look again:
Maybe Recipient -> FormTree m T.Text m Recipient
FormTree m0 v0 m0 Recipient
We are missing a Maybe Recipient
! From what I see above I guess you want to just ignore that argument and therefore we have:
recipientForm' :: (Monad m) => Formlet T.Text m Recipient
recipientForm' _ = Recipient <$> "email" .: text Nothing
which compiles just fine, yay :)