NAME

POE::Session::Cascading - Stack-like POE Sessions

AUTHOR

Matt Cashner (eek+cpan@eekeek.org)

DATE

$Date: 2005-12-07 01:58:36 -0500 (Wed, 07 Dec 2005) $

SYNOPSIS

    POE::Session::Cascading->new(
        name => 'foo',
        events => [
            'state1' => \&state1,
            'state2 => \&state2,
        ],
    );

    sub state1 {
        my %args = @_;
        $args{KERNEL}->post('somewhere','somestate');
        # [ snip ]
        
    }
    
    sub state2 {
        my %args = @_;
        # [ snip ]
        
        $args{SESSION}->stop;
    }

DESCRIPTION

INTRODUCTION

POE::Session::Cascading provides a stack-like session for POE. Another way of saying it is that a Cascading session is like a big switch statement. In the above example, when state1 is called in session foo, &state1 gets executed. When it finishes, state2 gets fired and &state2 gets executed. If state2 is called in session foo, only state2 will get executed.

CONTROLLING PROPOGATION

Each state can decide whether chain propogation should continue or not. If the state wishes to stop chain propogation, it must call $args{SESSION}->stop. Otherwise, chain propogation will continue. A state can call $args{SESSION}->go to forcibly allow chain propogation. This is largely superflous as this is the default option.

It would be appropriate to return call stop, for instance, if the state has determined that further action by this chain is unnecessary or undesirable. The state might launch a different chain and cal stop to shutdown the current chain's propogation.

LAUNCHING A CHAIN

To initiate a chain, post a call to the relevant state with the session's name. For instance, to activate the chain in the example above, one would write:

    $poe_kernel->post('foo','state1');

Arguments passes to POE's post method will be passed directly to the state and those which follow it.

WRITING A STATE

Cascading states are a bit different from the usual POE states, mainly in the argument list. Cascading states are passed a hash, containing three entries. SESSION contains a reference to the current session's object. KERNEL contains a reference to the POE kernel. ARGS contains an array reference of the arguments passed to the state.

Cascading states can do anything perl can. Cascading states are passed a hash, containing three entries. SESSION contains a reference to the current session's object. KERNEL contains a reference to the POE kernel. ARGS contains an array reference of the arguments passed to the state, including any data passed from the previous state..

METHODS

new()

    POE::Session::Cascading->new(
        name => 'foo',
        events => [
            step1 => \&step1,
            step2 => \&step2,
            step3 => \&step3,
        ]
    );

stop

    $args{SESSION}->stop;

Instruct the current session to stop chain propogation.

go

    $args{SESSION}->go;

Instruct the current session to continue chain propgation.

swap

    $args{SESSION}->swap($state1, $state2);
    

Reorder the event stack. Swap two states in the stack.

BUGS AND KNOWN ISSUES

• Cannot register or unregister a stack element at runtime

• Stack requires outside influence to start (is this actually a problem?)

LICENSE

Copyright (c) 2002, Matt Cashner. All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

• Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

• Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

• Neither the name of Matt Cashner nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

cpanm POE::Session::Cascading

perl -MCPAN -e shell
install POE::Session::Cascading