Hi boo_radley,
I've very much enjoyed your posts on this issue. I too am hacking together a crude prototype of web app system. Not quite as complex as yours, but I wanted to toss it into the mix. Sorry, few docs yet. And not much error checking. TT2 handles the HTML. I'm interested in comparing the two designs.

After thinking about this, an important issue is the topology of the graph of the page navigation. For example, is the (sub)site a simple linear directed graph? Easy. Is it a tree? Somewhat harder. If a page can send users different subsequent pages based on what they do, the validation code needs to be specific for not only where the person is coming from, but where they are headed. Example: suppose you have a page that has two forms on it: buy a house, or buy a car. (This is probably bad UI, but let's ignore that.) The car fields are irrelevant if the user is doing the house application, and vice versa. So the validation (provided valid address? provided mortgage insurance number? vs. provided valid make model year? valid VIN?) depends on the page the user is leaving (INITIAL APP SCREEN) as well as where they are headed (CAR APP II, HOME APP II). Perhaps this isn't a large concern, as the UI can (should) be simplified and where each page "does less".

Pardon the ramble, here's some code:

use strict;
use FindBin; use lib "$FindBin::Bin";  # push curdir onto @INC
use App;
use CGI qw(:cgi);
use CGI::Carp;
use Matrix::HTML;

my $app = App->new(tmpl_path=> '/templates');
$app->run(
      start => {
          TEMPLATE      => 'start.tt',
          TEMPLATE_VARS => sub {   #CODEREF OR HASH REF
          return {name=>'foo bar',
              size=>'big'}
          },
          PERSIST    => [qw(fred wilma betty)], #ARRAYREF
          VALIDATE   =>  sub {
          if (param('Color') eq 'Green') {
              croak "I hate green"
              }
          },
          POSTSUBMIT => sub{ print "HELLO!!!!!!"},
          NEXTPAGE   => sub {return 'two'}, #CODEREF or STRING
      }
      ,
      
      two => {
          TEMPLATE => 'two.tt',
          TEMPLATE_VARS => {
          x => Matrix::HTML->new([[431,442,3],[334,5,6],[7,8,4449]]),
          what_you_picked => param('Color'),
          size=>rand(10)
              
          }

      }
      );
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Here's the module, similar to CGI::Application:

package App;

use strict;
use CGI::Carp;
use CGI qw(:cgi);
use Template;
use FindBin;

sub new {
    my $class = shift;
    my $self = {
        tmpl_path   => '',
        mode_param  => 'rm',
        default_mode  => 'start'
        };
    bless($self, $class);
    # set default values
    my %parms = @_;
    foreach my $p (keys %parms) {$self->set($p, $parms{$p});}
    return $self;
    }

sub set {
    my ($self, $p, $v) = @_;
    croak "unknown parm: $p" unless exists($self->{$p});
    $self->{$p} = $v;
}

sub get {
    my ($self, $p) = @_;
    croak "unknown parm: $p" unless exists($self->{$p});
    return $self->{$p};
}

sub run {
    my ($self, %logic) = @_;
    my $nextmode;
    # figure out which page was just submitted
    my $mode = &param($self->get('mode_param'));
    if (defined($mode)) {
    # is this mode valid?
    croak "unknown mode: $mode" unless defined($logic{$mode});
    # determine next mode (coderef or string)
    if (ref($logic{$mode}{NEXTPAGE}) eq 'CODE') {
        $nextmode = &{$logic{$mode}{NEXTPAGE}};
    } else {
        $nextmode = $logic{$mode}{NEXTPAGE};
    }
    # run validator, if one exists (coderef)
    &{$logic{$mode}{VALIDATE}} if $logic{$mode}{VALIDATE};
    
    # run postsubmit, if one exists (coderef)
    &{$logic{$mode}{POSTSUBMIT}} if $logic{$mode}{POSTSUBMIT};
    
    } else {
    # if no mode specified, use default
    $nextmode = $self->get('default_mode');
    }

    # now work on next page
    $mode = $nextmode;

    # load template vars, if any (coderef or hashref)
    
    my $tmpl_vars;
    if (ref($logic{$mode}{TEMPLATE_VARS}) eq 'CODE') {
    $tmpl_vars = &{$logic{$mode}{TEMPLATE_VARS}};
    }
    if (ref($logic{$mode}{TEMPLATE_VARS}) eq 'HASH') {
    $tmpl_vars = $logic{$mode}{TEMPLATE_VARS};
    }

    # get the persistant variables (arrayref)
    my %hidden;
    foreach my $h (@{$logic{$nextmode}{PERSIST}}) {
    $hidden{$h}=param($h);
    }
    # and add in the runmode variable
    $hidden{$self->get('mode_param')} = $nextmode;

    # chunk into template vars
    $tmpl_vars->{hidden} = \%hidden;

    # set up the template object
    my $T = Template->new({
    INCLUDE_PATH =>$FindBin::Bin . $self->get('tmpl_path')
    });
    # get the name of the template file
    my $template = $logic{$nextmode}{TEMPLATE};
    # and spit out page
    $T->process($template, $tmpl_vars) || croak $T->error();
}

1;
[download]

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