Add toObservableUpdate

src/Quasar/Observable.hs

@@ -8,6 +8,7 @@ module Quasar.Observable (
   IsObservable(..),
   Observable(..),
   ObservableMessage(..),
+  toObservableUpdate,
   asyncObserve,
   asyncObserve_,
 
@@ -68,6 +69,12 @@ instance Applicative ObservableMessage where
   liftA2 fn (ObservableUpdate x) (ObservableUpdate y) = ObservableUpdate (fn x y)
 
 
+toObservableUpdate :: MonadThrow m => ObservableMessage a -> m (Maybe a)
+toObservableUpdate (ObservableUpdate value) = pure $ Just value
+toObservableUpdate ObservableLoading = pure Nothing
+toObservableUpdate (ObservableNotAvailable ex) = throwM ex
+
+
 class IsRetrievable v a | a -> v where
   retrieve :: MonadAsync m => a -> m (Task v)