NAME
asynchronous::universal::set_callback - declare trivial UNIVERSAL::set_callback and UNIVERSAL::callback_queue methods
SYNOPSIS
use asynchronous::universal::set_callback;
my $obj = bless [],"something nondeferred";
$obj->set_callback(sub{print @_}, "cheese!"); # prints "cheese!" immediatelyDESCRIPTION
This module adds set_callback($coderef,@arguments) and callback_queue methods to the UNIVERSAL class, that (1) immediately perform coderefs provided as arguments, rather than deferring them until a deferred object completes what its waiting for, since it's come back already, or wasn't deferred to start with; and (2) return an empty coderef, since a non-deferred object has no callback queue.
CONFORMANCE
In scenarios in which an asynchronous framework returns a placeholder object which becomes upgraded to a result object, multiple frameworks may peacefully coexist by using this module rather than each adding their own extension to UNIVERSAL.
behavior of set_callback method in conformant packages
Conformant asynchronous packages, either deferred-asynchronous or fully asynchronous, contain a set_callback method which queues a coderef for execution when the asynchronous operation is complete.
parameters to set_callback
A conformant package's set_callback method waits for the deferred operation to complete and then executes set_callback's first argument, which must be a coderef, with remaining arguments as arguments to the first. Arguments are copied rather than being passed by alias to avoid deferred action at a distance problems.
execution order of multiple callbacks
Conformant packages execute callbacks in the order that they are set, and deferred objects do not become ready until all callbacks have completed.
callback_queue method
Conformant packages provide a callback_queue method which returns an arrayref containing all callbacks that have been set on a deferred object, with $DeferredObject->callback_queue->[0] being the first in line. The nature of the representation of the callback queue is an implementation detail to the particular asynchronous framework, but they should be deletable and reorderable using splice, and a coder aware of the representation details of a particular framework can use the callback_queue method to manipulate a defered object's callback queue directly rather than calling set_callback.
UNIVERSAL::callback_queue returns an empty arrayref.
BUGS
UNIVERSAL methods are not invoked on the undefined value, or on non-blessed references.
HISTORY
SEE ALSO
asynchronous::universal::ready
AUTHOR
David Nicol <davidnico@cpan.org>
COPYRIGHT AND LICENSE
Copyright (C) 2005 David Nicol
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.6 or, at your option, any later version of Perl 5 you may have available.