NAME¶

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

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¶

    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.