NAME
   CGI::Application::Plugin::FormState - Store Form State without Hidden
   Fields

VERSION
   Version 0.10

SYNOPSIS
   FormState is just a temporary stash that you can use for storing and
   retrieving private parameters in your multi-page form.

       use CGI::Application::Plugin::FormState;

       my $form = <<EOF;
          <form action="app.cgi">
          <input type="hidden" name="run_mode" value="form_process_runmode">
          <input type="hidden" name="cap_form_state" value="<tmpl_var cap_form_state>">
          ...
          </form>
       EOF

       sub form_display_runmode {
           my $self = shift;

           # Store some parameters
           $self->form_state->param('name'       => 'Road Runner');
           $self->form_state->param('occupation' => 'Having Fun');

           my $t = $self->load_tmpl(scalarref => \$form);
           return $t->output;

       }

       sub form_process_runmode {
           my $self = shift;

           # Retrieve some parameters
           print $self->form_state->param('name');       # 'Road Runner'
           print $self->form_state->param('occupation'); # 'Having Fun'
       }

EXAMPLE
   This is a more complete example, using
   CGI::Application::Plugin::ValidateRM.

       use CGI::Application::Plugin::Session;
       use CGI::Application::Plugin::FormState;
       use CGI::Application::Plugin::ValidateRM;

       my $form = <<EOF;
          <form action="app.cgi">
          <input type="hidden" name="run_mode" value="my_form_process">
          <input type="hidden" name="cap_form_state" value="<tmpl_var cap_form_state>">
          ...
          </form>
       EOF

       sub my_form_display {
           my $self     = shift;
           my $errs     = shift;
           my $t        = $self->load_tmpl(scalarref => \$form);

           # Stash some data into it
           $self->form_state->param('name'       => 'Wile E. Coyote');
           $self->form_state->param('occupation' => 'Mining Engineer');

           # Normal ValidateRM error handling
           $t->param($errs) if $errs;
           return $t->output;
       }

       sub my_form_process {
           my $self;

           # Normal ValidateRM validation
           my ($results, $err_page) = $self->check_rm('my_form_display','_my_form_profile');
           return $err_page if $err_page;

           # The data from the submitted form
           my $params = $self->dfv_results;

           $params->{'name'}       = $self->form_state->param('name');       # 'Wile E. Coyote'
           $params->{'occupation'} = $self->form_state->param('occupation'); # 'Mining Engineer'

           # Now do something interesting with $params
           # ...

           my $t = $self->load_tmpl('success.html');
           return $t->output;
       }

       # Standard ValiateRM profile
       sub _my_form_profile {
           return {
               required => 'email',
               msgs => {
                       any_errors => 'some_errors',
                       prefix => 'err_',
               },
           };
       }

DESCRIPTION
   "CGI::Application::Plugin::FormState" provides a temporary storage area
   within the user's session for storing form-related data.

   The main use of this is for multi-page forms. Instead of using hidden
   fields to store data related to the form, you store and retrieve values
   from the form state.

   In the first instance of your app:

       $self->form_state->param('some_name' => 'some_value');
       $self->form_state->param('some_other_name' => 'some_other_value');

   And later, in a different instance of your app:

       $val1 = $self->form_state->param('some_name');
       $val2 = $self->form_state->param('some_other_name');

   To connect the first instance and the second, you put a single hidden
   field in your template:

       <input type="hidden" name="cap_form_state" value="<tmpl_var my_storage_name>">

   You don't have to worry about creating the template param
   "cap_form_state"; it is added automatically to your template parameters
   via the "load_tmpl" hook.

   If you want to use a parameter other than "cap_form_state" you can do so
   via the "name" parameter to "form_state-"config>.

   If you're skeptical about whether all this abstraction is a good idea,
   see "MOTIVATION", below.

PRESERVING FORM STATE ACROSS REDIRECTS
   You can include the form_state hash in a link:

       my $link = '/app.cgi?rm=list&cap_form_state=' . $self->form_state->id;

   If you use CGI::Application::Plugin::Redirect, you can easily create
   redirect this way:

       $self->redirect('/app.cgi?rm=list&cap_form_state=' . $self->form_state->id);

   If you also use CGI::Application::Plugin::LinkIntegrity it is as simple
   as:

       $self->redirect($self->link('/app.cgi', 'rm' => 'list', 'cap_form_state' => $self->form_state->id));

   Or, in the case of a link to the currently running app:

       $self->redirect($self->self_link('rm' => 'list', 'cap_form_state' => $self->form_state->id));

IMPLEMENTATION
   When you call "$self->form_state" for the first time, a top-level key is
   created in the user's session. This key contains a random, hard-to-guess
   element. It might look something like:

      form_state_cap_form_state_84eb13cfed01764d9c401219faa56d53

   All data you place in the form state with "param" is stored in the
   user's session under this key.

   You pass the name of this key on to the next instance of your
   application by means of a hidden field in your form:

       <input type="hidden" name="cap_form_state" value="<tmpl_var cap_form_state>">

   You manually put this hidden field in your template. The template
   parameter "cap_form_state" is automatically added to your template
   parameters via the "load_tmpl" hook. It contains the random,
   hard-to-guess portion (e.g. "84eb13cfed01764d9c401219faa56d53"). When
   the template is filled, the hidden field will look something like this:

       <input type="hidden" name="cap_form_state" value="84eb13cfed01764d9c401219faa56d53">

   Since all values are stored on the server in the user's session, the
   user can't tamper with any of them.

   To keep old form_data from cluttering up the user's session, the system
   uses CGI::Session's "expire" feature to expire old form state keys after
   a reasonable amount of time has passed (2 days by default).

   You can manually delete a form state storage by calling:

       $self->form_state->delete;

METHODS
   config(%options)
       Sets defaults for the plugin.

       Calling config is purely optional, since the defaults should be fine
       most purposes.

           $self->form_state->config('name' => 'storage_names', 'expires' => '3d')

       The following options are allowed:

       name
           Sets the name of the default form state storage. This name is
           used for the key in the user's session, for the name of hidden
           form field, and the template parameter used to fill the hidden
           form field. So if you set the "name" to "foo":

               $self->form_state_config('name' => 'foo');

           then the hidden field in your template should look like this:

               <input type="hidden" name="foo" value="<tmpl_var foo>">

           and the key in the user's session would look something like
           this:

              form_state_foo_84eb13cfed01764d9c401219faa56d53

       expires
           Indicates when form state storage keys should expire and
           disappear from the user's session. Uses the same format as
           CGI::Session's "expire". Defaults to 2 days ('2d'). To cancel
           expiration and make the form state last as long as the user's
           session does, use:

               $self->form_state_config('expires' => 0);

   param
       Read and set values in the form state storage. It acts like the
       "param" method typically does in modules such as CGI,
       CGI::Application, CGI::Session, "HTML::Template" etc.

           # set a value
           $self->form_state->param('some_name' => 'some_value');

           # retrieve a value
           my $val = $self->form_state->param('some_name');

           # set multiple values
           $self->form_state->param(
               'some_name'       => 'some_value',
               'some_other_name' => 'some_other_value',
           );

           # retrive the names of all the keys
           my @keys = $self->form_state->param;

   clear_params
       Clear all of the values in the form state storage:

          $self->form_state->param('name' => 'Road Runner');
          $self->form_state->clear_params;
          print $self->form_state->param('name'); # undef

   delete
       Deletes the form_state storage from the user's session.

   id  Returns the current value of the storage param - the "hard to guess"
       portion of the session key.

           my $id = $self->form_state->id;

   name
       Returns the current name being used for storage. Defaults to
       "cap_form_state".

           my $name = $self->form_state->name;

   session_key
       Returns the full key used for storage in the user's session.

           my $key = $self->form_state->session_key;

           # Get the full form state hash
           my $data = $self->session->param($key);

       The following can be used to debug the form_state data:

           use Data::Dumper;
           print STDERR Dumper $self->session->param($self->form_state->session_key);

MOTIVATION
 Why not just use hidden fields?
   Hidden fields are not secure. The end user could save a local copy of
   your form, change the hidden fields and tamper with your app's form
   state.

 Why not just use the user's session?
   With "CGI::Application::Plugin::FormState" the data is associated with a
   particular instance of a form, not with the user. If the user gives up
   halfway through your multi-page form, you don't want their session to be
   cluttered up with the incomplete form state data.

   If a user opens up your application in two browser windows (both sharing
   the same user session), each window should have it's own independent
   form state.

   For instance, in an email application the user might have one window
   open for the inbox and another open for the outbox. If you store the
   value of "current_mailbox" in the user's session, then one of these
   windows will go to the wrong mailbox.

   Finally, the user's session probably sticks around longer than the form
   state should.

AUTHOR
   Michael Graham, "<[email protected]>"

BUGS
   Please report any bugs or feature requests to
   "[email protected]", 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 Richard Dice and Cees Hek for helping me sort out the issues
   with this approach.

   The informative error message text used for when this module is loaded
   before your app actually @ISA "CGI::Application" object was stolen from
   Cees's CGI::Application::Plugin::TT module.

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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