Manual Reference Pages - POE::COMPONENT::PUBSUB (3)
POE::Component::PubSub - A generic publish/subscribe POE::Component that
enables POE::Sessions to publish events to which other POE::Sessions may
# Instantiate the publish/subscriber with the alias 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
# Publish an input event
$_[KERNEL]->post(pub, publish, BAR, +PUBLISH_INPUT, MyInputEvent);
# Tear down the whole thing
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 carpd, and the event returns without stopping
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.
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 doesnt 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.
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 carpd but execution will continue.
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.
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 carpd.
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.
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
This is the constructor for the publish subscribe component. It instantiates
its own session using the provided $alias argument to set its kernel alias.
If no alias is provided, the default alias is PUBLISH_SUBSCRIBE.
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().
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.
Nicholas R. Perez, <nperez at cpan.org>
Please report any bugs or feature requests to
bug-poe-component-pubsub at rt.cpan.org, or through the web interface at
I will be notified, and then youll automatically be notified of progress on
your bug as I make changes.
You can find documentation for this module with the perldoc command.
You can also look for information at:
COPYRIGHT & LICENSE
Copyright 2008-2009 Nicholas R. Perez, all rights reserved.
This program is released under the following license: gpl
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