Object::Pluggable(3) User Contributed Perl Documentation Object::Pluggable(3)NAMEObject::Pluggable - A base class for creating plugin-enabled objects
SYNOPSIS
# A simple POE Component that sends ping events to registered sessions
# and plugins every second.
{
package SimplePoCo;
use strict;
use warnings;
use base qw(Object::Pluggable);
use POE;
use Object::Pluggable::Constants qw(:ALL);
sub spawn {
my ($package, %opts) = @_;
my $self = bless \%opts, $package;
$self->_pluggable_init(
prefix => 'simplepoco_',
types => [qw(EXAMPLE)],
debug => 1,
);
POE::Session->create(
object_states => [
$self => { shutdown => '_shutdown' },
$self => [qw(_send_ping _start register unregister __send_event)],
],
);
return $self;
}
sub shutdown {
my ($self) = @_;
$poe_kernel->post($self->{session_id}, 'shutdown');
}
sub _pluggable_event {
my ($self) = @_;
$poe_kernel->post($self->{session_id}, '__send_event', @_);
}
sub _start {
my ($kernel, $self) = @_[KERNEL, OBJECT];
$self->{session_id} = $_[SESSION]->ID();
if ($self->{alias}) {
$kernel->alias_set($self->{alias});
}
else {
$kernel->refcount_increment($self->{session_id}, __PACKAGE__);
}
$kernel->delay(_send_ping => $self->{time} || 300);
return;
}
sub _shutdown {
my ($kernel, $self) = @_[KERNEL, OBJECT];
$self->_pluggable_destroy();
$kernel->alarm_remove_all();
$kernel->alias_remove($_) for $kernel->alias_list();
$kernel->refcount_decrement($self->{session_id}, __PACKAGE__) if !$self->{alias};
$kernel->refcount_decrement($_, __PACKAGE__) for keys %{ $self->{sessions} };
return;
}
sub register {
my ($kernel, $sender, $self) = @_[KERNEL, SENDER, OBJECT];
my $sender_id = $sender->ID();
$self->{sessions}->{$sender_id}++;
if ($self->{sessions}->{$sender_id} == 1) {
$kernel->refcount_increment($sender_id, __PACKAGE__);
$kernel->yield(__send_event => 'simplepoco_registered', $sender_id);
}
return;
}
sub unregister {
my ($kernel, $sender, $self) = @_[KERNEL, SENDER, OBJECT];
my $sender_id = $sender->ID();
my $record = delete $self->{sessions}->{$sender_id};
if ($record) {
$kernel->refcount_decrement($sender_id, __PACKAGE__);
$kernel->yield(__send_event => 'simplepoco_unregistered', $sender_id);
}
return;
}
sub __send_event {
my ($kernel, $self, $event, @args) = @_[KERNEL, OBJECT, ARG0..$#_];
return 1 if $self->_pluggable_process(EXAMPLE => $event, \@args) == PLUGIN_EAT_ALL;
$kernel->post($_, $event, @args) for keys %{ $self->{sessions} };
}
sub _send_ping {
my ($kernel, $self) = @_[KERNEL, OBJECT];
$kernel->yield(__send_event => 'simplepoco_ping', 'Wake up sleepy');
$kernel->delay(_send_ping => $self->{time} || 1);
return;
}
}
{
package SimplePoCo::Plugin;
use strict;
use warnings;
use Object::Pluggable::Constants qw(:ALL);
sub new {
my $package = shift;
return bless { @_ }, $package;
}
sub plugin_register {
my ($self, $pluggable) = splice @_, 0, 2;
print "Plugin added\n";
$pluggable->plugin_register($self, 'EXAMPLE', 'all');
return 1;
}
sub plugin_unregister {
print "Plugin removed\n";
return 1;
}
sub EXAMPLE_ping {
my ($self, $pluggable) = splice @_, 0, 2;
my $text = ${ $_[0] };
print "Plugin got '$text'\n";
return PLUGIN_EAT_NONE;
}
}
use strict;
use warnings;
use POE;
my $pluggable = SimplePoCo->spawn(
alias => 'pluggable',
time => 1,
);
POE::Session->create(
package_states => [
main => [qw(_start simplepoco_registered simplepoco_ping)],
],
);
$poe_kernel->run();
sub _start {
my $kernel = $_[KERNEL];
$kernel->post(pluggable => 'register');
return;
}
sub simplepoco_registered {
print "Main program registered for events\n";
my $plugin = SimplePoCo::Plugin->new();
$pluggable->plugin_add('TestPlugin', $plugin);
return;
}
sub simplepoco_ping {
my ($heap, $text) = @_[HEAP, ARG0];
print "Main program got '$text'\n";
$heap->{got_ping}++;
$pluggable->shutdown() if $heap->{got_ping} == 3;
return;
}
DESCRIPTIONObject::Pluggable is a base class for creating plugin enabled objects.
It is a generic port of POE::Component::IRC's plugin system.
If your object dispatches events to listeners, then Object::Pluggable
may be a good fit for you.
Basic use would involve subclassing Object::Pluggable, then overriding
"_pluggable_event()" and inserting "_pluggable_process()" wherever you
dispatch events from.
Users of your object can then load plugins using the plugin methods
provided to handle events generated by the object.
You may also use plugin style handlers within your object as
"_pluggable_process()" will attempt to process any events with local
method calls first. The return value of these handlers has the same
significance as the return value of 'normal' plugin handlers.
PRIVATE METHODS
Subclassing Object::Pluggable gives your object the following 'private'
methods:
"_pluggable_init"
This should be called on your object after initialisation, but before
you want to start processing plugins. It accepts a number of
argument/value pairs:
'types', an arrayref of the types of events that your poco will support,
OR a hashref with the event types as keys and their abbrevations
(used as plugin event method prefixes) as values. This argument is
mandatory.
'prefix', the prefix for your events (default: 'pluggable_');
'reg_prefix', the prefix for the register()/unregister() plugin methods
(default: 'plugin_');
'debug', a boolean, if true, will cause a warning to be printed every time a
plugin call fails.
Notes: 'prefix' should probably end with a '_'. The types specify the
prefixes for plugin handlers. You can specify as many different types
as you require.
"_pluggable_destroy"
This should be called from any shutdown handler that your poco has. The
method unloads any loaded plugins.
"_pluggable_process"
This should be called before events are dispatched to interested
sessions. This gives pluggable a chance to discard events if requested
to by a plugin.
The first argument is a type, as specified to "_pluggable_init()".
sub _dispatch {
my ($self, $event, $type, @args) = @_;
# stuff
my $type = ...
return 1 if $self->_pluggable_process($type, $event, \@args)) == PLUGIN_EAT_ALL;
# dispatch event to interested sessions.
}
A reference to the argument array is passed. This allows the plugin
system to mangle the arguments or even add new ones.
"_pluggable_event"
This method should be overridden in your class so that pipeline can
dispatch events through your event dispatcher. Pipeline sends a
prefixed 'plugin_add' and 'plugin_del' event whenever plugins are added
or removed, respectively. A prefixed 'plugin_error' event will be sent
if a plugin a) raises an exception, b) fails to return a true value
from its register/unregister methods, or c) fails to return a valid EAT
constant from a handler.
sub _pluggable_event {
my $self = shift;
$poe_kernel->post($self->{session_id}, '__send_event', @_);
}
There is an example of this in the SYNOPSIS.
PUBLIC METHODS
Subclassing Object::Pluggable gives your object the following public
methods:
"pipeline"
Returns the Object::Pluggable::Pipeline object.
"plugin_add"
Accepts two arguments:
The alias for the plugin
The actual plugin object
Any number of extra arguments
The alias is there for the user to refer to it, as it is possible to
have multiple plugins of the same kind active in one Object::Pluggable
object.
This method goes through the pipeline's "push()" method, which will
call "$plugin->plugin_register($pluggable, @args)".
Returns the number of plugins now in the pipeline if plugin was
initialized, "undef"/an empty list if not.
"plugin_del"
Accepts the following arguments:
The alias for the plugin or the plugin object itself
Any number of extra arguments
This method goes through the pipeline's "remove()" method, which will
call "$plugin->plugin_unregister($pluggable, @args)".
Returns the plugin object if the plugin was removed, "undef"/an empty
list if not.
"plugin_get"
Accepts the following arguments:
The alias for the plugin
This method goes through the pipeline's "get()" method.
Returns the plugin object if it was found, "undef"/an empty list if
not.
"plugin_list"
Takes no arguments.
Returns a hashref of plugin objects, keyed on alias, or an empty list
if there are no plugins loaded.
"plugin_order"
Takes no arguments.
Returns an arrayref of plugin objects, in the order which they are
encountered in the pipeline.
"plugin_register"
Accepts the following arguments:
The plugin object
The type of the hook (the hook types are specified with _pluggable_init()'s 'types')
The event name[s] to watch
The event names can be as many as possible, or an arrayref. They
correspond to the prefixed events and naturally, arbitrary events too.
You do not need to supply events with the prefix in front of them, just
the names.
It is possible to register for all events by specifying 'all' as an
event.
Returns 1 if everything checked out fine, "undef"/an empty list if
something is seriously wrong.
"plugin_unregister"
Accepts the following arguments:
The plugin object
The type of the hook (the hook types are specified with _pluggable_init()'s 'types')
The event name[s] to unwatch
The event names can be as many as possible, or an arrayref. They
correspond to the prefixed events and naturally, arbitrary events too.
You do not need to supply events with the prefix in front of them, just
the names.
It is possible to register for all events by specifying 'all' as an
event.
Returns 1 if all the event name[s] was unregistered, undef if some was
not found.
PLUGINS
The basic anatomy of a pluggable plugin is:
# Import the constants, of course you could provide your own
# constants as long as they map correctly.
use Object::Pluggable::Constants qw( :ALL );
# Our constructor
sub new {
...
}
# Required entry point for pluggable plugins
sub plugin_register {
my($self, $pluggable) = @_;
# Register events we are interested in
$pluggable->plugin_register($self, 'SERVER', qw(something whatever));
# Return success
return 1;
}
# Required exit point for pluggable
sub plugin_unregister {
my($self, $pluggable) = @_;
# Pluggable will automatically unregister events for the plugin
# Do some cleanup...
# Return success
return 1;
}
sub _default {
my($self, $pluggable, $event) = splice @_, 0, 3;
print "Default called for $event\n";
# Return an exit code
return PLUGIN_EAT_NONE;
}
As shown in the example above, a plugin's "_default" subroutine (if
present) is called if the plugin receives an event for which it has no
handler.
The special exit code CONSTANTS are documented in
Object::Pluggable::Constants. You could provide your own as long as the
values match up, though.
TODO
Better documentation >:]
AUTHOR
Chris 'BinGOs' Williams <chris@bingosnet.co.uk>
LICENSE
Copyright "(c)" Chris Williams, Apocalypse, Hinrik Oern Sigur`sson and
Jeff Pinyan
This module may be used, modified, and distributed under the same terms
as Perl itself. Please see the license that came with your Perl
distribution for details.
KUDOS
APOCAL for writing the original POE::Component::IRC plugin system.
japhy for writing POE::Component::IRC::Pipeline which improved on it.
All the happy chappies who have contributed to POE::Component::IRC over
the years (yes, it has been years) refining and tweaking the plugin
system.
The initial idea was heavily borrowed from X-Chat, BIG thanks go out to
the genius that came up with the EAT_* system :)
SEE ALSO
POE::Component::IRC
Object::Pluggable::Pipeline
Both POE::Component::Client::NNTP and POE::Component::Server::NNTP use
this module as a base, examination of their source may yield further
understanding.
perl v5.14.1 2010-10-09 Object::Pluggable(3)
