[dancer-users] Question about the Dancer2 tutorial under Windows/Apache as an app...

31 May 2015

      Perl Dancer Community:

I am converting from Dancer to Dancer2 (better late than never) and also
developing some preliminary curriculum materials for CoderDojo using Perl
Dancer2 as a framework for web development.

I started with SawyerX's tutorial page:

   http://search.cpan.org/~xsawyerx/Dancer2/lib/Dancer2/Tutorial.pod

The "dancr.pl" tutorial program ran just fine under the port 3000 server
and the tutorial was useful and instructive:

C:\Users\CoderDojo\Perl\Dancer\dancr>perl dancr.pl
...
...
Dancer2 v0.160001 server 2496 listening on http://0.0.0.0:3000
I ran into an issue when I tried to convert this demo into an app that
would run under Apache in a Windows environment, however.

The *crux* of the issue is that the "$flash message" does not work in the
app (I suspect because the global variable $flash and the two subroutines
are not part of a route, but I could *really* use an explanation, if this
issue is obvious to someone:

I created the app as normal:

C:\Apache24\htdocs>*dancer2 -a dancr*
+ dancr
+ dancr\config.yml
+ dancr\cpanfile
+ dancr\Makefile.PL
+ dancr\MANIFEST.SKIP
+ dancr\bin
+ dancr\bin\app.psgi
+ dancr\environments
+ dancr\environments\development.yml
+ dancr\environments\production.yml
+ dancr\lib
+ dancr\lib\dancr.pm
+ dancr\public
+ dancr\public\dispatch.cgi
+ dancr\public\dispatch.fcgi
+ dancr\public\404.html
+ dancr\public\500.html
+ dancr\public\favicon.ico
+ dancr\public\css
+ dancr\public\css\error.css
+ dancr\public\css\style.css
+ dancr\public\images
+ dancr\public\images\perldancer-bg.jpg
+ dancr\public\images\perldancer.jpg
+ dancr\public\javascripts
+ dancr\public\javascripts\jquery.js
+ dancr\t
+ dancr\t\001_base.t
+ dancr\t\002_index_route.t
+ dancr\views
+ dancr\views\index.tt
+ dancr\views\layouts
+ dancr\views\layouts\main.tt

With the resulting app files, I added the code from the original "dancr.pl"
demo to the applications "dancr.pm" module:

package dancr;
use Dancer2;

our $VERSION = '0.1';

get '/' => sub {
    template 'index';
};

true;

I had to make the following adjustments to the code for Windows/Apache:

(1) Change the session to YAML

#set 'session'      => 'Simple';
set 'session'      => 'YAML';

(2) Adjust the path for request->base:

#   $tokens->{'css_url'} = request->base . 'css/dancr.css';
    $tokens->{'css_url'} = request->base . '/css/dancr.css';

Everything with the app works as expected *except* for the "$flash message"
code:

my $flash;

sub set_flash($message) {
    my $message = shift;

    $flash = $message;
}

sub get_flash {
    my $message = $flash;
    $flash = '';

    return $message;
}

I suspect that since these subs are outside a route, perhaps I'm getting an
effect about the scope of the variables... but calls to these subroutines
do *not* set $flash or $message as expected:

   template 'show_entries.tt', {
   'msg' => get_flash,

   set_flash('New entry posted!');

   set_flash('You are logged in.');

   set_flash('You are logged out.');

For each of these, the $flash variable (which is a free-standing global in
the module) is never set... and so the get_flash sub never returns a value.

-- 
Prairie Nyx
prairienyx@gmail.com