haskell - Yesod generateFormPost - No instance for (RenderMessage master0 FormMessage) -


i tried follow screencast michael snoyman http://vimeo.com/39646807. however, seems changes i18n causes code fail. can't find information on how solve problem on scaffolded site , can't quite make sense of information given here http://www.yesodweb.com/book/internationalization.

this error get, referring code in home.hs:

no instance (rendermessage master0 formmessage)   arising use of `generateformpost' possible fix:   add instance declaration (rendermessage master0 formmessage) in stmt of 'do' block:   (formwidget, enctype) <- generateformpost noteform in expression:   { (formwidget, enctype) <- generateformpost noteform;        defaultlayout ($(widgetfile "notes")) } in equation `getnotesr':     getnotesr       = { (formwidget, enctype) <- generateformpost noteform;              defaultlayout ($(widgetfile "notes")) }

the information seems pretty clear, problem can't figure out how add instance declaration (rendermessage master0 formmessage).

here's code added home.hs

noteform = renderbootstrap $ note     <$> areq textfield "title" nothing     <*> areq textfield "content" nothing  getnotesr =     (formwidget, enctype) <- generateformpost noteform     defaultlayout $(widgetfile "notes")  postnotesr = return () getnoter noteid = return ()

ant following templates/notes.hamlet

<form method=post enctype=#{enctype}>     ^{formwidget}     <input type=submit>

as general proposition, when see this:

no instance (rendermessage master0 formmessage)

bear in mind master0 (or starting lowercase letter) free type variable has not been instantiated concrete type. can mentally replace a if helps. see message says there's no generic rendermessage instance uniquely determined formmessage in second parameter , arbitrary type in first parameter.

therefore, usual way fix figure out want instantiate free type to, , provide type signature or other hint fix instantiation.

in case, type signature suggested michael snoyman noteform :: form note serves purpose.


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