Fun with dynamics

Main.hs

example
  :: MonadWidget t m
  => Dynamic t Thing
  -> m (Dynamic t ValidThing)
example dyThing =
  return $ runMaybeT $ do -- the Dynamic monad
    name <- lift (thing_name <$> dyThing)
    
    -- Name must be non-empty
    guard $ name /= ""
    
    ValidThing <$> pure name
               <*> lift (thing_property dyThing)