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POE::Session::MessageBased - a message-based (not @_
based) POE::Session
use POE::Kernel;
use POE::Session::MessageBased;
( inline_states =>
{ _start => sub {
my $message = shift;
print "Started.\n";
$message->kernel->yield( count => 2 );
count => sub {
my ($message, $count) = @_;
print "Counted to $count.\n";
if ($count < 10) {
$message->kernel->yield( count => ++$count );
_stop => sub {
print "Stopped.\n";
POE::Session::MessageBased exists mainly to replace
@_[KERNEL, etc.] with message objects that encapsulate
various aspects of each event. It also exists as an exam-
ple of a subclassed POE::Session, in case someone wants to
create new callback or Session semantics.
People generally balk at the @_[KERNEL, etc.] calling con-
vention that POE uses by default. The author defends the
position that this calling convention is a simple combina-
tion of common Perl features. Interested people can read for a more
detailed account.
Anyway, POE::Session::MessageBased subclasses POE::Session
and works almost identically to it. The major change is
the way event handlers (states) are called.
Inline (coderef) handlers gather their parameters like
my ($message, @args) = @_;
Package and object-oriented handlers receive an additional
parameter representing the package or object. This is
part of the common calling convention that Perl uses.
my ($package, $message, @args) = @_; # Package states.
my ($self, $message, @args) = @_; # Object states.
The $message parameter is an instance of
POE::Session::Message, which is not documented elsewhere.
POE::Session::Message encapsulates every POE parameter and
provides accessors for them.
POE::Session POE::Session::MessageBased
------------------------ -----------------------------------
$_[OBJECT] $package, or $self
$_[SESSION] $message->session
$_[KERNEL] $message->kernel
$_[HEAP] $message->heap
$_[STATE] $message->state
$_[SENDER] $message->sender
$_[CALLER_FILE] $message->caller_file
$_[CALLER_LINE] $message->caller_line
@_[ARG0..$#_] $message->args (in list context)
You do not need to use POE::Session::Message yourself. It
is included in POE::Session::MessageBased itself.
$message->args() always returns a list: @_[ARG0..$#_]. It
would be nice to return a list reference in scalar con-
POE::Session::MessageBased is Copyright 2002-2010 by Rocco
Caputo. All rights are reserved. POE::Session::Message-
Based is free software; you may redistribute it and/or
modify it under the same terms as Perl itself.
The author may be contacted by e-mail via
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