On Thu, Nov 8, 2012 at 9:16 AM, Jeremy Shaw <jer
...@n-heptane.com> wrote:
> reform does not validate fields, it validates forms. And forms are built
> by combining other forms together. At the bottom we have a bunch of forms
> that contain only one field such as inputText, select, textarea, etc.
> For something like confirming a password, we can create a form like this:
> password :: AuthForm v Text
> password =
> errorList ++> (((,) <$> password1 <*> password2)
> `transformEither` samePassword) `transformEither` minLength 6
> That will create a form with two password fields. Then it uses
> transformEither to confirm that both fields are the same, and if so,
> returns their value, otherwise it returns a validation error. It also
> checks that the password is at least 6 characters long. That password form
> can then be used in the overall account create form. Here is the complete
> example:
> newAccountForm :: (Functor v, MonadIO v) => AcidState AuthState ->
> AuthForm v (AuthId, UserPassId)
> newAccountForm authStateH =
> (R.fieldset
> (errorList ++>
> (R.ol $ (((,) <$> username <*> password <* submitButton)))
> `transformEitherM`
> createAccount))
> where
> submitButton = R.li $ (mapView (\html -> html ! A.class_ "submit")
> $ inputSubmit "Create Account")
> username = R.li $ errorList ++> ((label ("username: " :: String)
> ++> inputText mempty) `transformEither` (minLength 1))
> password1 = R.li $ label ("password: " :: String) ++>
> inputPassword
> password2 = R.li $ label ("confirm password: " :: String) ++>
> inputPassword
> password =
> errorList ++> (((,) <$> password1 <*> password2)
> `transformEither` samePassword) `transformEither` minLength 6
> samePassword (p1, p2) =
> if p1 /= p2
> then (Left $ PasswordMismatch)
> else (Right p1)
> createAccount (username, password) =
> do passHash <- liftIO $ mkHashedPass password
> r <- update' authStateH $ CreateUserPass (UserName
> username) passHash
> -- fixme: race condition
> case r of
> (Left e) -> return (Left $ UPE e)
> (Right userPass) ->
> do authId <- update' authStateH (NewAuthMethod
> (AuthUserPassId (upId userPass)))
> return (Right (authId, upId userPass))
> The <select> variation is a bit trickier. There is no reason why the
> validation can not be done correctly on the server-side, but for a system
> like that, it seems like you might also want to have some clientside
> actions happening. For example, disabling/hiding the 'forbidden' actions
> via javascript.
> Right now that would require you to manually attach an onchange handler to
> the select element to enable/disable other fields. Which is possible.. just
> not elegant.
> reform (and similar libraries) are great for web 1.0. Making things more
> web 2.0 is still largely unexplored. Though I am hoping that things like
> Fay will open the doors to making things like client-side validation easier.
> - jeremy
> On Wed, Nov 7, 2012 at 11:57 PM, Richard Wallace <
> rwall...@thewallacepack.net> wrote:
>> Hello,
>> Today I have a question on how to do validation when some fields depend
>> on the value of others. For instance, take the simple example of a signup
>> or change password form, where you have 2 password fields, both of which
>> must be non-empty and have the same value.
>> Or, as a more complicated example, say you have a form with a <select>
>> element and based on the users selection, some fields may become required,
>> optional, or even forbidden.
>> Is there a good way to represent this kind of field value dependent
>> validation in reform? I can't see any obvious way, the proof system is
>> cool, but seems limited to just inspecting the value of a one field at a
>> time.
>> Thanks,
>> Rich
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