| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
UnliftIO.Resource
Contents
Description
Unlifted Control.Monad.Trans.Resource .
Since: 1.1.10
Synopsis
- runResourceT :: MonadUnliftIO m => ResourceT m a -> m a
- liftResourceT :: MonadIO m => ResourceT IO a -> ResourceT m a
- allocateU :: ( MonadUnliftIO m, MonadResource m) => m a -> (a -> m ()) -> m ( ReleaseKey , a)
- data ResourceT m a
- data ReleaseKey
- class MonadIO m => MonadResource m
- register :: MonadResource m => IO () -> m ReleaseKey
- release :: MonadIO m => ReleaseKey -> m ()
- unprotect :: MonadIO m => ReleaseKey -> m ( Maybe ( IO ()))
- allocate :: MonadResource m => IO a -> (a -> IO ()) -> m ( ReleaseKey , a)
UnliftIO variants
runResourceT :: MonadUnliftIO m => ResourceT m a -> m a Source #
Unlifted version of
runResourceT
.
Since: 1.1.10
liftResourceT :: MonadIO m => ResourceT IO a -> ResourceT m a Source #
Lifted version of
liftResourceT
.
Since: 1.1.10
allocateU :: ( MonadUnliftIO m, MonadResource m) => m a -> (a -> m ()) -> m ( ReleaseKey , a) Source #
Unlifted
allocate
.
Since: 1.2.6
Reexports
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
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
Instances
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
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
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
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
register
ing the release action, but this properly handles masking of
asynchronous exceptions.
Since 0.3.0