The Resource transformer. This transformer keeps track of all registered actions, and calls them upon exit (via runResourceT). Actions may be registered via register, or resources may be allocated atomically via allocate. allocate corresponds closely to bracket.

Releasing may be performed before exit via the release function. This is a highly recommended optimization, as it will ensure that scarce resources are freed early. Note that calling release will deregister the action, so that a release action will only ever be called once.

Since 0.3.0

Instances

Instances details

MonadTrans ResourceT Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods lift :: Monad m => m a -> ResourceT m a #
MonadRWS r w s m => MonadRWS r w s (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal
MonadError e m => MonadError e (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods throwError :: e -> ResourceT m a # catchError :: ResourceT m a -> (e -> ResourceT m a) -> ResourceT m a #
MonadReader r m => MonadReader r (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods ask :: ResourceT m r # local :: (r -> r) -> ResourceT m a -> ResourceT m a # reader :: (r -> a) -> ResourceT m a #
MonadState s m => MonadState s (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods get :: ResourceT m s # put :: s -> ResourceT m () # state :: (s -> (a, s)) -> ResourceT m a #
MonadWriter w m => MonadWriter w (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods writer :: (a, w) -> ResourceT m a # tell :: w -> ResourceT m () # listen :: ResourceT m a -> ResourceT m (a, w) # pass :: ResourceT m (a, w -> w) -> ResourceT m a #
MonadFail m => MonadFail (ResourceT m) Source #	Since: 1.2.2
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods fail :: String -> ResourceT m a #
MonadFix m => MonadFix (ResourceT m) Source #	Since: 1.1.8
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods mfix :: (a -> ResourceT m a) -> ResourceT m a #
MonadIO m => MonadIO (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods liftIO :: IO a -> ResourceT m a #
Alternative m => Alternative (ResourceT m) Source #	Since 1.1.5
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods empty :: ResourceT m a # (<\|>) :: ResourceT m a -> ResourceT m a -> ResourceT m a # some :: ResourceT m a -> ResourceT m [a] # many :: ResourceT m a -> ResourceT m [a] #
Applicative m => Applicative (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods pure :: a -> ResourceT m a # (<>) :: ResourceT m (a -> b) -> ResourceT m a -> ResourceT m b # liftA2 :: (a -> b -> c) -> ResourceT m a -> ResourceT m b -> ResourceT m c # (>) :: ResourceT m a -> ResourceT m b -> ResourceT m b # (<*) :: ResourceT m a -> ResourceT m b -> ResourceT m a #
Functor m => Functor (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods fmap :: (a -> b) -> ResourceT m a -> ResourceT m b # (<$) :: a -> ResourceT m b -> ResourceT m a #
Monad m => Monad (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods (>>=) :: ResourceT m a -> (a -> ResourceT m b) -> ResourceT m b # (>>) :: ResourceT m a -> ResourceT m b -> ResourceT m b # return :: a -> ResourceT m a #
MonadPlus m => MonadPlus (ResourceT m) Source #	Since 1.1.5
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods mzero :: ResourceT m a # mplus :: ResourceT m a -> ResourceT m a -> ResourceT m a #
MonadCatch m => MonadCatch (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods catch :: (HasCallStack, Exception e) => ResourceT m a -> (e -> ResourceT m a) -> ResourceT m a #
MonadMask m => MonadMask (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods mask :: HasCallStack => ((forall a. ResourceT m a -> ResourceT m a) -> ResourceT m b) -> ResourceT m b # uninterruptibleMask :: HasCallStack => ((forall a. ResourceT m a -> ResourceT m a) -> ResourceT m b) -> ResourceT m b # generalBracket :: HasCallStack => ResourceT m a -> (a -> ExitCase b -> ResourceT m c) -> (a -> ResourceT m b) -> ResourceT m (b, c) #
MonadThrow m => MonadThrow (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods throwM :: (HasCallStack, Exception e) => e -> ResourceT m a #
MonadCont m => MonadCont (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods callCC :: ((a -> ResourceT m b) -> ResourceT m a) -> ResourceT m a #
PrimMonad m => PrimMonad (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Associated Types type PrimState (ResourceT m) # Methods primitive :: (State# (PrimState (ResourceT m)) -> (# State# (PrimState (ResourceT m)), a #)) -> ResourceT m a #
MonadIO m => MonadResource (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods liftResourceT :: ResourceT IO a -> ResourceT m a Source #
MonadUnliftIO m => MonadUnliftIO (ResourceT m) Source #	Since: 1.1.10
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods withRunInIO :: ((forall a. ResourceT m a -> IO a) -> IO b) -> ResourceT m b #
type PrimState (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal type PrimState (ResourceT m) = PrimState m

data ReleaseKey Source #

A lookup key for a specific release action. This value is returned by register and allocate, and is passed to release.

Since 0.3.0

class MonadIO m => MonadResource m Source #

A Monad which allows for safe resource allocation. In theory, any monad transformer stack which includes a ResourceT can be an instance of MonadResource.

Note: runResourceT has a requirement for a MonadUnliftIO m monad, which allows control operations to be lifted. A MonadResource does not have this requirement. This means that transformers such as ContT can be an instance of MonadResource. However, the ContT wrapper will need to be unwrapped before calling runResourceT.

Since 0.3.0

Minimal complete definition

liftResourceT

Instances

Instances details

MonadIO m => MonadResource (ResourceT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods liftResourceT :: ResourceT IO a -> ResourceT m a Source #
MonadResource m => MonadResource (MaybeT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods liftResourceT :: ResourceT IO a -> MaybeT m a Source #
MonadResource m => MonadResource (ExceptT e m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods liftResourceT :: ResourceT IO a -> ExceptT e m a Source #
MonadResource m => MonadResource (IdentityT m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods liftResourceT :: ResourceT IO a -> IdentityT m a Source #
MonadResource m => MonadResource (ReaderT r m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods liftResourceT :: ResourceT IO a -> ReaderT r m a Source #
MonadResource m => MonadResource (StateT s m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods liftResourceT :: ResourceT IO a -> StateT s m a Source #
MonadResource m => MonadResource (StateT s m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods liftResourceT :: ResourceT IO a -> StateT s m a Source #
(Monoid w, MonadResource m) => MonadResource (WriterT w m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods liftResourceT :: ResourceT IO a -> WriterT w m a Source #
(Monoid w, MonadResource m) => MonadResource (WriterT w m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods liftResourceT :: ResourceT IO a -> WriterT w m a Source #
MonadResource m => MonadResource (ContT r m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods liftResourceT :: ResourceT IO a -> ContT r m a Source #
(Monoid w, MonadResource m) => MonadResource (RWST r w s m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods liftResourceT :: ResourceT IO a -> RWST r w s m a Source #
(Monoid w, MonadResource m) => MonadResource (RWST r w s m) Source #
Instance details Defined in Control.Monad.Trans.Resource.Internal Methods liftResourceT :: ResourceT IO a -> RWST r w s m a Source #

release :: MonadIO m => ReleaseKey -> m () Source #

Call a release action early, and deregister it from the list of cleanup actions to be performed.

Since 0.3.0

allocate Source #

Arguments

:: MonadResource m
=> IO a	allocate
-> (a -> IO ())	free resource
-> m (ReleaseKey, a)

Perform some allocation, and automatically register a cleanup action.

This is almost identical to calling the allocation and then registering the release action, but this properly handles masking of asynchronous exceptions.

Since 0.3.0

register :: MonadResource m => IO () -> m ReleaseKey Source #

Register some action that will be called precisely once, either when runResourceT is called, or when the ReleaseKey is passed to release.

Since 0.3.0

unprotect :: MonadIO m => ReleaseKey -> m (Maybe (IO ())) Source #

Unprotect resource from cleanup actions; this allows you to send resource into another resourcet process and reregister it there. It returns a release action that should be run in order to clean resource or Nothing in case if resource is already freed.

Since 0.4.5