How to get post data in yesod?

Question

Hello I want to manually insert a data in the table and also i used the lookupPostParam.

here's the code in Posting a New News.

      postNewsR :: Handler Html
      postNewsR = do
                now <- liftIO getCurrentTime
                newsTitle <- lookupPostParam "title"
                newsUrl <- lookupPostParam "news_url"
                newsSnapshot <- lookupPostParam "news_snopshot"
                newsArea <- lookupPostParam "news_area"
                newsSubject <- lookupPostParam "news_subject"
                newsContent <- lookupPostParam "news_content"

               newsId <- runDB $ insert News newsTitle newsUrl newsSnapshot newsContent False Nothing now Nothing

              redirect NewsR

but it gives me this Following error:

      Couldn't match type ‘Control.Monad.Trans.Reader.ReaderT
                   (PersistEntityBackend
                      (Data.Text.Internal.Text
                       -> Data.Text.Internal.Text
                       -> Data.Text.Internal.Text
                       -> Data.Text.Internal.Text
                       -> Bool
                       -> Maybe Int
                       -> UTCTime
                       -> Maybe UTCTime
                       -> News))
                   m0
                   (Key
                      (Data.Text.Internal.Text
                       -> Data.Text.Internal.Text
                       -> Data.Text.Internal.Text
                       -> Data.Text.Internal.Text
                       -> Bool
                       -> Maybe Int
                       -> UTCTime
                       -> Maybe UTCTime
                       -> News))’
          with ‘Maybe Data.Text.Internal.Text
                -> Maybe Data.Text.Internal.Text
                -> Maybe Data.Text.Internal.Text
                -> Maybe Data.Text.Internal.Text
                -> Bool
                -> Maybe a0
                -> UTCTime
                -> Maybe a1
                -> Control.Monad.Trans.Reader.ReaderT
                     (YesodPersistBackend App) (HandlerT App IO) t0’
         Expected type: Maybe Data.Text.Internal.Text
           -> Maybe Data.Text.Internal.Text
           -> Maybe Data.Text.Internal.Text
           -> Maybe Data.Text.Internal.Text
           -> Bool
           -> Maybe a0
           -> UTCTime
           -> Maybe a1
           -> YesodDB App t0
         Actual type: Control.Monad.Trans.Reader.ReaderT
             (PersistEntityBackend
                (Data.Text.Internal.Text
                 -> Data.Text.Internal.Text
                 -> Data.Text.Internal.Text
                 -> Data.Text.Internal.Text
                 -> Bool
                 -> Maybe Int
                 -> UTCTime
                 -> Maybe UTCTime
                 -> News))
             m0
             (Key
                (Data.Text.Internal.Text
                 -> Data.Text.Internal.Text
                 -> Data.Text.Internal.Text
                 -> Data.Text.Internal.Text
                 -> Bool
                 -> Maybe Int
                 -> UTCTime
                 -> Maybe UTCTime
                 -> News))
      The function insert is applied to 9 arguments,
      but its type ‘(Data.Text.Internal.Text
           -> Data.Text.Internal.Text
           -> Data.Text.Internal.Text
           -> Data.Text.Internal.Text
           -> Bool
           -> Maybe Int
           -> UTCTime
           -> Maybe UTCTime
           -> News)
          -> Control.Monad.Trans.Reader.ReaderT
               (PersistEntityBackend
                  (Data.Text.Internal.Text
                   -> Data.Text.Internal.Text
                   -> Data.Text.Internal.Text
                   -> Data.Text.Internal.Text
                   -> Bool
                   -> Maybe Int
                   -> UTCTime
                   -> Maybe UTCTime
                   -> News))
               m0
               (Key
                  (Data.Text.Internal.Text
                   -> Data.Text.Internal.Text
                   -> Data.Text.Internal.Text
                   -> Data.Text.Internal.Text
                   -> Bool
                   -> Maybe Int
                   -> UTCTime
                   -> Maybe UTCTime
                   -> News))’

I hope you help me, Thanks in advance

EDIT:

---

I change something in my code. here's the update. From lookupPostParam to runInputPost

    newsTitle <- runInputPost $ ireq textField "title"
    newsUrl <- runInputPost $ ireq textField "news_url"
    newsSnapshot <- runInputPost $ ireq textField "news_snopshot"
    newsArea <- runInputPost $ ireq textField "news_snopshot"
    newsSubject <- runInputPost $ ireq textField "news_snopshot"
    newsContent <- runInputPost $ ireq textareaField "news_content"

    -- Inserting it to the table News
    newsId <- insert $ News newsTitle newsUrl newsSnapshot newsContent False Nothing now Nothing

Now it gives me 2 error:

 1. Couldn't match type ‘Control.Monad.Trans.Reader.ReaderT
                   SqlBackend m0’
          with ‘HandlerT App IO’
    Expected type: HandlerT App IO (Key News)
    Actual type: Control.Monad.Trans.Reader.ReaderT
             SqlBackend m0 (Key News) …

Thanks in advance.

Answer 1

It would be helpful to see how you've defined your News entity...

Let's take a look at the signature of the function in question:

lookupPostParam :: (MonadResource m, MonadHandler m)
                => Text
                -> m (Maybe Text)

That says lookupPostParam takes a Text argument, returns a Maybe Text, and lives in the m monad. When you invoke lookupPostParam, the <- keyword unwraps the m monad for us. So newsTitle in

newsTitle <- lookupPostParam "title"

has the type Maybe Text. I would imagine your News defines its fields as Text types, so you still have to handle the Maybe before you will have values you can insert in your database. E.g.,

case newsTitle of
 Nothing -> redirect NewsR -- and handle the error, return 400 perhaps
 Just title -> do
   newsUrl <- lookupPostParam "news_url"
   case newsUrl of
    Nothing -> redirect NewsR -- and handle the error
    Just url -> do
      -- and so on

Once you've unwrapped Maybe from the return values of lookupPostParam, you should have no trouble applying them to insert.

newsId <- runDB $ insert $ 
          News title url snapshot content False Nothing now Nothing

Take a look at Data.Maybe or reply back here if you're still stuck.