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, "<mag-perl@occamstoothbrush.com>"

BUGS
    Please report any bugs or feature requests to
    "bug-cgi-application-plugin-formstate@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 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.