Hi Francisco, There's a few issues at play here, all of which should be addressed in the documentation. As a historical note, I should mention that I had actually dropped support for the CRUD module a bit ago, and added it back by request. It works, but isn't very customizable. If you're not scared off by that, read on! The first problem (the error message you're getting) is because mkToForm is not meant to be called like that. Instead, you need to call it after the entity definitions as its own TH splice, like so: mkToForm (undefined :: Entry) Now, GHC will complain about a stage restriction. Basically, there are certain things you can't refer to from TH in the same file in which they were defined, and type class instances is one of them. The solution is to move the entity declaration to a separate file (Model.hs, attached). Next, defaultCrud can't be passed as-is to the routing system, since it gives no indication what datatype should be used. Instead, you need to define one that uses explicit types: entryCrud :: Blog -> Crud Blog Entry entryCrud = defaultCrud And then pass that to the routing: /admin AdminR EntryCrud entryCrud The only other thing I changed was fixing the indentation in getRootR, though I'm guessing that was a copy-paste issue. I also didn't fix it particularly well, I leave that as an exercise to the reader ;). HTH, Michael On Tue, Apr 5, 2011 at 7:57 PM, Francisco Jose CHAVES ALONSO < pachopepe@gmail.com> wrote:
Hi
In order to know how the CRUD works, I was trying the blog example of the Screencast, updated to yesod 7 but the mkToForm gives me the following error:
No instance for (PersistEntity [Database.Persist.Base.EntityDef]) arising from a use of `mkToForm' Possible fix: add an instance declaration for (PersistEntity [Database.Persist.Base.EntityDef]) In the expression: mkToForm In the first argument of `share', namely `[mkToForm, mkPersist, mkMigrate "migrateAll"]' In the expression: share [mkToForm, mkPersist, mkMigrate "migrateAll"] [Database.Persist.Base.EntityDef "Entry" [] [("title", "String", []), ("day", "Day", ["Desc"]), ....] [] []]
Any suggestion?
Thanks in advance
Francisco
The code is:
{-# LANGUAGE TypeFamilies, QuasiQuotes, GeneralizedNewtypeDeriving, TemplateHaskell, MultiParamTypeClasses #-} import Yesod import Yesod.Helpers.Crud import Database.Persist import Database.Persist.Sqlite import Database.Persist.TH import Data.Time (Day) import Network.Wai.Middleware.Debug (debug) import Network.Wai.Handler.Warp (run)
share [mkToForm, mkPersist, mkMigrate "migrateAll"] [persist| Entry title String day Day Desc content Html deriving |]
-- Necesary for CRUD instance Item Entry where itemTitle = entryTitle
data Blog = Blog { pool :: ConnectionPool }
type EntryCrud = Crud Blog Entry
mkYesod "Blog" [parseRoutes| / RootR GET /entry/#EntryId EntryR GET -- Subsite /admin AdminR EntryCrud defaultCrud |]
instance Yesod Blog where approot _ = "http://localhost:3000"
instance YesodPersist Blog where type YesodDB Blog = SqlPersist runDB db = liftIOHandler $ fmap pool getYesod >>= runSqlPool db
getRootR = do entries <- runDB $ selectList [] [EntryDayDesc] 0 0 defaultLayout $ do setTitle $ string "Yesod Blog Tutorial Homepage" [hamlet| <h1> Archive <ul> $forall entry <- entries <li> <a href="@{EntryR (fst entry)}">#{entryTitle (snd entry)} <p> <a href="@{AdminR CrudListR}">Admin |]
getEntryR entryid = do entry <- runDB $ get404 entryid defaultLayout $ do setTitle $ string $ entryTitle entry [hamlet| <h1> #{entryTitle entry} <h2> #{show (entryDay entry)} #{entryContent entry} |]
withBlog :: (Application -> IO a) -> IO a withBlog f = withSqlitePool "blog.db3" 8 $ \pool -> do flip runSqlPool pool $ do (runMigration migrateAll) insert $ Entry "First Entry" (read "2011-04-04") $ preEscapedString "<h3>First Entry</h3>" let h = Blog pool toWaiApp h >>= f
main = withBlog $ run 3000 . debug
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