Why?

Because IMO, the main reason for using templates is to seperate code from markup. The code produces some data. The markup displays the data. Those Application Frameworks don't seem to be too good at seperating code and markup (I have to admit though, that I know next to nothing about them, only that they are too big/powerfull). After all, they embed code in markup.

So I am looking for a "pipeline"-type, Just-Template System, which reduces the number of available modules somewhat.

The best-known contestors here are TemplateToolkit resp. Apache::Template and HTML::Template. But if you look at there manpages, you'll quickly find references to stuff like "TPL_LOOP" (HTML::Template). TT2 even has it's own mini-language. So, once again, code (even rather trivial) mixed with the markup.

There is one module, CGI::FastTemplate, that does seperate code from markup completly. But the way different templates are strung together seems rather comlicated to me.

But why is there no Templating System with a clean seperation of code and markup?

There are two types of code (at least) that pollute nearly all Templating Systems:

• Loops

  Loops are one of the things computers do best (for very good reasons, mainly lazyness of humans). So, a template should be able to handle large amounts of similar data using ... a template. Obvious. So a Templating System must handle Loops. Most (all?) do it by adding some sort of LOOP or FOREACH Syntax, thereby introducing code into the markup. But there is another way to loop over data: Recursion.

• If-Blocks As the template is rather general, you want it to handle slightly different kinds of data differently. One very obvious example would be to print something like "No Data" instead of "undef". Or to highlight the current item in a list.

  Often IF-Blocks are also used to present different kinds of data differently, which can lead to long series of IF-ELSIF-ELSE blocks. Which is a clear pointer that one should use Object Orientation instead.

  Another way would be to add something like attributes to the data. But as far as I know, attributes aren't included that thightly into Perl as OO.

So I am looking for a Templating System that does Just Templating, no code in the markup, maybe by using recursion and OO.

I didn't find anything.

So I am proposing this:

Template::YetAnother

The name is just a placeholder right now, other ideas are:

• Template::Dumper
• Template::Stringify
• Template::OO
• Template::OO_Dumper
• any other ideas?

Template::YetAnother is yet another Templating module, using a slightly different approach than most of the other Templating modules.

The templates are completly dumb. There is absolutly no piece of code in a template - neither Perl nor "mini language". A template consists of arbitrary text (e.g. HTML) and Template Tags, e.g. % title %

Your application builds up a data structure. The data structure consists of various Perl Data Types (Strings, Arrays, Hashes) and Template::YetAnother Objects (or Data Structures marked with some other kind of metainformation, e.g. with attributes)

The data structure gets passed to Template::YetAnother, which magically find the right template for each object and replaces all Template Tags (recursivly) with the dumped/stringified data structure.

Template::YetAnother is like Data::Dumper on steroids. It's the big Stringifyer.

Template::YetAnother doesn't use one monolithic template, but a lot of small template fragments, each one correlating to a data type generated by the application.

Template::YetAnother is just an idea right now. I am trying the "write documentation, write tests, write code" way of development... There is only a small prove-of-concept type bit of code (I can send it/post it if somebody cares..). I'll really appreciate feedback on this.

I hope that this descripction is clear enought. If not, let me know and I'll post some clarification / examples.

SYNOPSIS

    
  # generate a new template handler
  my $th=Template::YetAnother->new
              ({
                namespace=>'acme',
                template_dir=>'/projects/acme/templates/',
               });
  # build up a data structure
  $data={
         title=>$th->title('this is the title'),
         breadcrumb=>[
          $th->link({url=>'/index.html',text=>'Home'}),
          $th->separator_breadcrumb,
          $th->link({url=>'/acme/index.html',text=>'Acme'}),
          $th->separator_breadcrumb,
          $th->link({url=>'/acme/bleach.html',text=>'Bleach'}),
                     ],
         content=>[
           $th->element({heading=>'SYNOPSIS',value=>'blabla'}),
            $th->element({heading=>'DESCRIPTION',value=>'foo bar'}),
                  ],
         lastmod=>scalar localtime,

        };

   # fill template & print
   print $th->fill({data=>$data});



   ##################################################
   # for this to work, we need the following files in
   # /projects/acme/templates


   # file: main.tpl
   <html><head><title>[% title %]</title></head>
   <body>
   <center>[% breadcrumb %]</center>
   <h1>[% title %]</h1>
   [% content %]
   <hr>
   [% lastmod %]


   # file: link.tpl
   <a href='[% url %]'>[% text %]</a>


   # file: seperator.tpl
    /


   # file: element.tpl
   <h3>[% heading %]</h3>;
   <p>[% value %]</p>;


   ##################################################
   # the finished template should look like this:


   <html><head><title>this is the title</title></head>
   <body>
   <center>
   <a href='/index.html'>Home</a> /
   <a href='/acme/index.html'>Acme</a> /
   <a href='/acme/bleach.html'>Bleach</a>
   </center>
   <h1>this is the title</h1>
   <h3>SYNOPSIS<h3>
   <p>blabla</p>;
   <h3>DESCRIPTION</h3>
   <p>foo bar</p>
   <hr>
   Thu Nov  7 21:51:05 200
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DESCRIPTION

new

      my $th=Template::YetAnother->new({
                                template_dir=>'/path/to/templates/',
                                # namespace=>'projectname',
                                # start_tag=>'<--',
                                # end_tag=>  '-->',
                                });
[download]

Generates a new Template::YetAnother Handler Object.

fill

      $th->fill($data);
[download]

Fill the template with the data in the data structure.

_gen

      my $fragment=$th->_gen('type',$data)
[download]

Generates a new Template Fragment

You usually do not have to call this. You just say

      $th->type($data)
[download]

and AUTOLOAD passes it to "_gen"

SEE ALSO

Search for "template" on http://search.cpan.org, if you dare.

--
#!/usr/bin/perl
for(ref bless{},just'another'perl'hacker){s-:+-$"-g&&print$_.$/}
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