Future::AsyncAwait::AwUserbContributed Perl Future::AsyncAwait::Awaitable(3pm)
NAME
"Future::AsyncAwait::Awaitable" - the interface required by
"Future::AsyncAwait"
DESCRIPTION
This module documents the method interface required by
"Future::AsyncAwait" to operate on future instances returned by
expressions invoked by the "await" keyword, and returned by functions
declared by "async sub". This information is largely of relevance to
implementors of other module integrations, event systems, or similar.
It is not necessary to make regular use of the syntax provided by the
module when working with existing event systems.
The methods required by this interface are all capitalised and prefixed
with "AWAIT_...", ensuring they are unlikely to clash with existing
methods on a class which may have differing semantics.
Role::Tiny
If Role::Tiny is available, this module declares itself to be a role
that requires the following named methods. The role supplies no code to
the applied class, but can be useful for checking that you have in fact
implemented all of the required methods.
Conformance Test
To assist implementors of alternative future-like classes, an API
conformance test suite is provided by
Test::Future::AsyncAwait::Awaitable. You may find this useful to check
that your implementation is suitable.
CONSTRUCTORS
The following methods are expected to create new future instances. They
make use of the class set by the prevailing "future_class" import
argument, if set, or default to "Future" if not.
AWAIT_NEW_DONE
Generate a new immediate future that is successful. The future will
already be ready and have the list of values set as its result.
$f = $CLASS->AWAIT_NEW_DONE( @results )
# $f->AWAIT_IS_READY will be true
# $f->AWAIT_GET will return @results
AWAIT_NEW_FAIL
Generate a new immediate future that is failed. The future will already
be ready and invoking the "AWAIT_GET" method will throw the given
exception.
$f = $CLASS->AWAIT_NEW_FAIL( $message )
# $f->AWAIT_IS_READY will be true
# $f->AWAIT_GET will throw $message
INSTANCE METHODS
AWAIT_CLONE
Generate a new pending future of the same type as an existing one,
which is not modified by doing so. It will only be invoked on instances
that are currently pending.
$new_f = $f->AWAIT_CLONE
If the instance has any fields that are required for successful
operation (such as application-wide context or event system components)
these ought to be copied. The method should not otherwise copy any per-
instance state such as pending callbacks or partial results.
AWAIT_DONE
Sets the success result of an existing still-pending future. It will
only be invoked on future instances that are currently pending.
$f->AWAIT_DONE( @results )
# $f->AWAIT_IS_READY will now be true
# $f->AWAIT_GET will now return @results
AWAIT_FAIL
Sets the failure result of an existing still-pending future. It will
only be invoked on future instances that are currently pending.
$f->AWAIT_FAIL( $message )
# $f->AWAIT_IS_READY will now be true
# $f->AWAIT_GET will now throw $message
AWAIT_IS_READY
Returns true if a future is ready (successful, failed or cancelled);
false if still pending.
$bool = $f->AWAIT_IS_READY
AWAIT_IS_CANCELLED
Returns true is a future has already been cancelled; false if still
pending, successful or failed.
$bool = $f->AWAIT_IS_CANCELLED
An implementation that does not support cancellation can simply return
a constant false here:
sub AWAIT_IS_CANCELLED { 0 }
AWAIT_GET
Yields the result of a successful future (or just the first value if
called in scalar context). Throws the failure message as an exception
if called on a a failed one. Will not be invoked on a pending or
cancelled future.
@result = $f->AWAIT_GET
$result = $f->AWAIT_GET
$f->AWAIT_GET
AWAIT_ON_READY
Attach a new CODE reference to be invoked when the future becomes ready
(by success or failure). The arguments and context that $code is
invoked with are unspecified.
$f->AWAIT_ON_READY( $code )
AWAIT_CHAIN_CANCEL
Attach a future instance to be cancelled when another one is cancelled.
$f1->AWAIT_CHAIN_CANCEL( $f2 )
When $f1 is cancelled, then $f2 is cancelled. There is no link from $f2
back to $f1 - whenever $f2 changes state here, nothing special happens
to $f1.
An implementation that does not support cancellation can simply ignore
this method.
sub AWAIT_CHAIN_CANCEL { }
An older version of this API specification named this
"AWAIT_ON_CANCEL", but that name will be repurposed for attaching code
blocks in a later version.
AWAIT_ON_CANCEL
Attach a new CODE reference to be invoked when the future is cancelled.
$f->AWAIT_ON_CANCEL( $code )
An implementation that does not support cancellation can simply ignore
this method.
sub AWAIT_ON_CANCEL { }
AWAIT_WAIT
Called by the toplevel "await" expression in order to run the event
system and wait for the instance to be ready. It should return results
or throw an exception in the same manner as "AWAIT_GET".
@result = $f->AWAIT_WAIT
$result = $f->AWAIT_WAIT
$f->AWAIT_WAIT
AUTHOR
Paul Evans <leonerd@leonerd.org.uk>
perl v5.36.0 2023-02-12Future::AsyncAwait::Awaitable(3pm)
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