GenEvent

Event Handling Principles

See: Erlang gen_event Behaviour

GenEvent Typeclass

class GenEvent e st | e -> st, st -> e where
  handleEvent :: HandleEvent e st

Event Manager Example

module Demo.Event
  ( Event(..)
  , start
  , notify
  ) where
import Prelude
import Control.Behaviour.GenEvent
  ( class GenEvent
  , Init
  , initOk
  , HandleEvent
  , startLinkWith
  )
import Control.Behaviour.GenEvent as E
data Event = EventA | EventB
data State = State [Event]
instance GenEvent Event State where
  handleEvent = handleEvent
name :: Atom
name = :event
start :: Process Pid
start = startLinkWith name init
notify :: Event -> Process ()
notify = E.notify name
init :: Init State
init = initOk (State [])
handleEvent :: HandleEvent Event State
handleEvent e (State events) = do
  println "Event"
  return $ State [e|events]

Start a Event Manager process

-- | Start a standalone Event Manager process.
start :: forall e st. GenEvent e st => (Init st) -> Process Pid
startWith :: forall e st. GenEvent e st => Name -> (Init st) -> Process Pid
-- | Start a Event Manager process as part of a supervision tree.
startLink :: forall e st. GenEvent e st => (Init st) -> Process Pid
startLinkWith :: forall e st. GenEvent e st => Name -> (Init st) -> Process Pid

Init callback

data InitResult st
  = InitOk st
  | InitOkHib st
  | InitError ExitReason
-- | Init callback
type Init st = Process (InitResult st)

HandleEvent Callback

-- | HandleEvent callback
type HandleEvent e st = e -> st -> Process st

Client APIs

notify :: forall e. Name -> e -> Process ()
syncNotify :: forall e. Name -> e -> Process ()