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