Maintainer	Bas van Dijk <v.dijk.bas@gmail.com>

Control.Monad.Trans.Region.OnExit

Description

This module is not intended for end-users. It should only be used by library authors wishing to extend this regions library.

Synopsis

Documentation

type Finalizer = IO ()Source

An IO computation that closes or finalizes a resource. For example "hClose someHandle" or "free somePtr".

data FinalizerHandle r Source

A handle to a Finalizer that allows you to duplicate it to a parent region using dup.

Duplicating a finalizer means that instead of it being performed when the current region terminates it is performed when the parent region terminates.

Instances

Dup FinalizerHandle

onExit :: MonadIO pr => Finalizer -> RegionT s pr (FinalizerHandle (RegionT s pr))Source

Register the Finalizer in the region. When the region terminates all registered finalizers will be perfomed if they're not duplicated to a parent region.

Note that finalizers are run in LIFO order (Last In First Out). So executing the following:

runRegionT $ do
  _ <- onExit $ putStrLn "finalizer 1"
  _ <- onExit $ putStrLn "finalizer 2"
  return ()

yields:

finalizer 2
finalizer 1