src/Reflex/TriggerEvent/Class.hs · patch

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1-- | This module defines 'TriggerEvent', which describes actions that may create

2-- new 'Event's that can be triggered from 'IO'.

3{-# LANGUAGE FlexibleInstances #-}

4{-# LANGUAGE FunctionalDependencies #-}

5{-# LANGUAGE MultiParamTypeClasses #-}

6{-# LANGUAGE UndecidableInstances #-}

7module Reflex.TriggerEvent.Class

8 ( TriggerEvent (..)

9 ) where

11import Reflex.Class

13import Control.Monad.Reader

15--TODO: Shouldn't have IO hard-coded

16-- | 'TriggerEvent' represents actions that can create 'Event's that can be

17-- triggered by 'IO' actions.

18class Monad m => TriggerEvent t m | m -> t where

19 -- | Create a triggerable 'Event'. Whenever the resulting function is called,

20 -- the resulting 'Event' will fire at some point in the future. Note that

21 -- this may not be synchronous.

22 newTriggerEvent :: m (Event t a, a -> IO ())

23 -- | Like 'newTriggerEvent', but the callback itself takes another callback,

24 -- to be invoked once the requested 'Event' occurrence has finished firing.

25 -- This allows synchronous operation.

26 newTriggerEventWithOnComplete :: m (Event t a, a -> IO () -> IO ()) --TODO: This and newTriggerEvent should be unified somehow

27 -- | Like 'newTriggerEventWithOnComplete', but with setup and teardown. This

28 -- relatively complex type signature allows any external listeners to be

29 -- subscribed lazily and then removed whenever the returned 'Event' is no

30 -- longer being listened to. Note that the setup/teardown may happen multiple

31 -- times, and there is no guarantee that the teardown will be executed

32 -- promptly, or even at all, in the case of program termination.

33 newEventWithLazyTriggerWithOnComplete :: ((a -> IO () -> IO ()) -> IO (IO ())) -> m (Event t a)

35instance TriggerEvent t m => TriggerEvent t (ReaderT r m) where

36 newTriggerEvent = lift newTriggerEvent

37 newTriggerEventWithOnComplete = lift newTriggerEventWithOnComplete

38 newEventWithLazyTriggerWithOnComplete = lift . newEventWithLazyTriggerWithOnComplete