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Manual Reference Pages  -  CGI::APPLICATION::PLUGIN::FORWARD (3)

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NAME

CGI::Application::Plugin::Forward - Pass control from one run mode to another

CONTENTS

VERSION

Version 1.06

SYNOPSIS



    use base CGI::Application;
    use CGI::Application::Plugin::Forward;

    sub setup {
        my $self = shift;
        $self->run_modes([qw(
            start
            second_runmode
        )]);
    }
    sub start {
        my $self = shift;
        return $self->forward(second_runmode);
    }
    sub second_runmode {
        my $self = shift;

        my $rm = $self->get_current_runmode;  # second_runmode

    }



DESCRIPTION

The forward method passes control to another run mode and returns its output. This is equivalent to calling $self->$other_runmode, except that CGI::Application’s internal value of the current run mode is updated.

This means that calling $self->get_current_runmode after calling forward will return the name of the new run mode. This is useful for modules that depend on the name of the current run mode such as CGI::Application::Plugin::AnyTemplate.

For example, here’s how to pass control to a run mode named other_action from start while updating the value of current_run_mode:



    sub setup {
        my $self = shift;
        $self->run_modes({
            start         => start,
            other_action  => other_method,
        });
    }
    sub start {
        my $self = shift;
        return $self->forward(other_action);
    }
    sub other_method {
        my $self = shift;

        my $rm = $self->get_current_runmode;  # other_action
    }



Note that forward accepts the name of the run mode (in this case ’other_action’), which might not be the same as the name of the method that handles the run mode (in this case ’other_method’)

You can still call $self->other_method directly, but current_run_mode will not be updated:



    sub setup {
        my $self = shift;
        $self->run_modes({
            start         => start,
            other_action  => other_method,
        });
    }
    sub start {
        my $self = shift;
        return $self->other_method;
    }
    sub other_method {
        my $self = shift;

        my $rm = $self->get_current_runmode;  # start
    }



Forward will work with coderef-based runmodes as well:



    sub setup {
        my $self = shift;
        $self->run_modes({
            start         => start,
            anon_action   => sub {
                my $self = shift;
                my $rm = $self->get_current_runmode;  # anon_action
            },
        });
    }
    sub start {
        my $self = shift;
        return $self->forward(anon_action);
    }



FORWARD vs. REDIRECT

Calling forward changes the run mode of your application, but it stays within the same HTTP request.

To redirect to a new runmode using a completely new web request, you might consider using the redirect method provided by CGI::Application::Plugin::Redirect.

The advantage of using an external redirect as opposed to an internal forward is that it provides a ’clean break’ between pages.

For instance, in a typical BREAD application (Browse, Read, Edit, Add, Delete), after the user completes an action, you usually return the user to the Browse list. For instance, when the user adds a new record via a POST form, and your app returns them to the list of records.

If you use forward, then you are still in the same request as the original add record. The user might hit reload, expecting to refresh the list of records. But in fact, reload will attempt to repost the add record form. The user’s browser might present a warning about reposting the same data. The browser may refuse to redisplay the page, due for caching reasons.

So in this case, it may make more sense to do a fresh HTTP redirect back to the Browse list.

METHODS

    forward

Runs another run mode passing any parameters you supply. Returns the output of the new run mode.



    return $self->forward(run_mode_name, @run_mode_params);



HOOKS

Before the forwarded run mode is called, the forward_prerun hook is called. You can use this hook to do any prep work that you want to do before any new run mode gains control.

This is similar to CGI::Application’s built in cgiapp_prerun method, but it is called each time you call forward; not just the when your application starts.



    sub setup {
        my $self = shift;
        $self->add_callback(forward_prerun => \&prepare_rm_stuff);
    }

    sub prepare_rm_stuff {
        my $self = shift;
        # do any necessary prep work here....
    }



Note that your hooked method will only be called when you call forward. If you never call forward, the hook will not be called. In particuar, the hook will not be called for your application’s start_mode. For that, you still use cgiapp_prerun.

If you want to have a method run for every run mode including the start_mode, then you can call the hook directly from cgiapp_prerun.



    sub setup {
        my $self = shift;
        $self->add_callback(forward_prerun => \&prepare_rm_stuff);
    }
    sub cgiapp_prerun {
        my $self = shift;
        $self->prepare_rm_stuff;
    }

    sub prepare_rm_stuff {
        my $self = shift;
        # do any necessary prep work here....
    }



Alternately, you can hook cgiapp_prerun to the forward_prerun hook:



    sub setup {
        my $self = shift;
        $self->add_callback(forward_prerun => \&cgiapp_prerun);
    }
    sub cgiapp_prerun {
        my $self = shift;
        # do any necessary prep work here....
    }



This is a less flexible solution, since certain things that can be done in cgiapp_prerun (like setting prerun_mode) won’t work when the method is called from the forward_prerun hook.

AUTHOR

Michael Graham, <mag-perl@occamstoothbrush.com>

BUGS

Please report any bugs or feature requests to bug-cgi-application-plugin-forward@rt.cpan.org, or through the web interface at <http://rt.cpan.org>. I will be notified, and then you’ll automatically be notified of progress on your bug as I make changes.

ACKNOWLEDGEMENTS

Thanks to Mark Stosberg for the idea and...well...the implementation as well.

COPYRIGHT & LICENSE

Copyright 2005 Michael Graham, All Rights Reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

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perl v5.20.3 CGI::APPLICATION::PLUGIN::FORWARD (3) 2016-03-17

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