| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Capnp.Rpc.Promise
Description
This module defines a Promise type, represents a value which is not yet
available, and related utilities.
Synopsis
- data Promise a
- data Fulfiller a
- newPromise :: MonadSTM m => m (Promise a, Fulfiller a)
- newPromiseWithCallback :: MonadSTM m => (Either Exception a -> STM ()) -> m (Promise a, Fulfiller a)
- newCallback :: MonadSTM m => (Either Exception a -> STM ()) -> m (Fulfiller a)
- fulfill :: MonadSTM m => Fulfiller a -> a -> m ()
- breakPromise :: MonadSTM m => Fulfiller a -> Exception -> m ()
- data ErrAlreadyResolved = ErrAlreadyResolved
- wait :: MonadSTM m => Promise a -> m a
Documentation
A promise is a value that may not be ready yet.
Creating promises
newPromise :: MonadSTM m => m (Promise a, Fulfiller a) Source #
Create a new promise and an associated fulfiller.
newPromiseWithCallback :: MonadSTM m => (Either Exception a -> STM ()) -> m (Promise a, Fulfiller a) Source #
Create a new promise which also excecutes an STM action when it is resolved.
newCallback :: MonadSTM m => (Either Exception a -> STM ()) -> m (Fulfiller a) Source #
Like newPromiseWithCallback, but doesn't return the promise.
Fulfilling or breaking promises
fulfill :: MonadSTM m => Fulfiller a -> a -> m () Source #
Fulfill a promise by supplying the specified value. It is an error to
call fulfill if the promise has already been fulfilled (or broken).
breakPromise :: MonadSTM m => Fulfiller a -> Exception -> m () Source #
Break a promise. When the user of the promise executes wait, the
specified exception will be raised. It is an error to call breakPromise
if the promise has already been fulfilled (or broken).
data ErrAlreadyResolved Source #
An exception thrown if breakPromise or fulfill is called on an
already-resolved fulfiller.
Constructors
| ErrAlreadyResolved |
Instances
| Show ErrAlreadyResolved Source # | |
Defined in Capnp.Rpc.Promise Methods showsPrec :: Int -> ErrAlreadyResolved -> ShowS # show :: ErrAlreadyResolved -> String # showList :: [ErrAlreadyResolved] -> ShowS # | |
| Exception ErrAlreadyResolved Source # | |
Defined in Capnp.Rpc.Promise Methods toException :: ErrAlreadyResolved -> SomeException # fromException :: SomeException -> Maybe ErrAlreadyResolved # | |