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