NAME¶
POE::Component::PubSub - A generic publish/subscribe POE::Component that enables
POE::Sessions to publish events to which other POE::Sessions may subscribe.
VERSION¶
Version 0.04
SYNOPSIS¶
# Instantiate the publish/subscriber with the alias "pub"
POE::Component::PubSub->new('pub');
# Publish an event called "FOO". +PUBLISH_OUTPUT is actually optional.
$_[KERNEL]->post('pub', 'publish', 'FOO', +PUBLISH_OUTPUT);
# Elsewhere, subscribe to that event, giving it an event to call # when the
published event is fired. $_[KERNEL]->post('pub', 'subscribe', 'FOO',
'FireThisEvent');
# Fire off the published event $_[KERNEL]->post('pub', 'FOO');
# Publish an 'input' event $_[KERNEL]->post('pub', 'publish', 'BAR',
+PUBLISH_INPUT, 'MyInputEvent');
# Tear down the whole thing $_[KERNEL]->post('pub', 'destroy');
EVENTS¶
All public events do some sanity checking to make sure of a couple of things
before allowing the events such as checking to make sure the posting session
actually owns the event it is publishing, or that the event passed as the
return event during subscription is owned by the sender. When one of those
cases comes up, an error is carp'd, and the event returns without stopping
execution.
- 'publish'
- This is the event to use to publish events. It accepts one
argument, the event to publish. The published event may not already be
previously published. The event may be completely arbitrary and does not
require the publisher to implement that event. Think of it as a name for a
mailing list.
You can also publish an 'input' or inverse event. This allows for arbitrary
sessions to post to your event. In this case, you must supply the optional
published event type and the event to be called when the published event
fires.
There are two types: PUBLISH_INPUT and PUBLISH_OUTPUT. PUBLISH_OUPUT is
implied when no argument is supplied.
- 'subscribe'
- This is the event to use when subscribing to published
events. It accepts two arguments: 1) the published event, and 2) the event
name of the subscriber to be called when the published event is fired. The
event doesn't need to be published prior to subscription to resolve
chicken and egg problems in an async environment. But, the sender must own
and implement the return event.
- 'rescind'
- Use this event to stop publication of an event. It accepts
one argument, the published event. The event must be published, and
published by the sender of the rescind event. If the published event has
any subscribers, a warning will be carp'd but execution will
continue.
- 'cancel'
- Cancel subscriptions to events with this event. It accepts
one argment, the published event. The event must be published and the
sender must be subscribed to the event.
- '_default'
- After an event is published, the publisher may arbitrarily
fire that event to this component and the subscribers will be notified by
calling their respective return events with whatever arguments are passed
by the publisher. The event must be published, owned by the publisher, and
have subscribers for the event to be propagated. If any of the subscribers
no longer has a valid return event their subscriptions will be cancelled
and a warning will be carp'd.
- 'listing'
- To receive an array reference containing tuples of the
event name, and the type of the events that are currently published within
the component, call this event. It accepts one argument, the return event
to fire with the listing. The sender must own the return event.
- 'destroy'
- This event will simply destroy any of its current state and
remove any and all aliases this session may have picked up. This should
free up the session for garbage collection.
CLASS METHODS¶
- POE::Component::PubSub->new($alias)
- This is the constructor for the publish subscribe
component. It instantiates it's own session using the provided $alias
argument to set its kernel alias. If no alias is provided, the default
alias is 'PUBLISH_SUBSCRIBE'.
DEBUGGING¶
- $POE::Component::PubSub::TRACE_AND_DEBUG
- To enable debugging within the component at the
POE::Session level and also with various warnings, set this variable to
logical true BEFORE calling new().
NOTES¶
Right now this component is extremely simple, but thorough when it comes to
checking the various requirements for publishing and subscribing. Currently,
there is no mechanism to place meta-subscriptions to the events of the
component itself. This feature is planned for the next release.
Also, to do some of the checking on whether subscribers own the return events,
some ideas were lifted from POE::API::Peek, and like that module, if there are
changes to the POE core, they may break this module.
AUTHOR¶
Nicholas R. Perez, "<nperez at cpan.org>"
BUGS¶
Please report any bugs or feature requests to "bug-poe-component-pubsub at
rt.cpan.org", or through the web interface at
<
http://rt.cpan.org/NoAuth/ReportBug.html?Queue=POE-Component-PubSub>. I
will be notified, and then you'll automatically be notified of progress on
your bug as I make changes.
SUPPORT¶
You can find documentation for this module with the perldoc command.
perldoc POE::Component::PubSub
You can also look for information at:
- •
- AnnoCPAN: Annotated CPAN documentation
<http://annocpan.org/dist/POE-Component-PubSub>
- •
- CPAN Ratings
<http://cpanratings.perl.org/d/POE-Component-PubSub>
- •
- RT: CPAN's request tracker
<http://rt.cpan.org/NoAuth/Bugs.html?Dist=POE-Component-PubSub>
- •
- Search CPAN
<http://search.cpan.org/dist/POE-Component-PubSub>
COPYRIGHT & LICENSE¶
Copyright 2008-2009 Nicholas R. Perez, all rights reserved.
This program is released under the following license: gpl