HTML::Template::FAQ(3) Frequently Asked Questions about HTML::Template

SYNOPSIS

In the interest of greater understanding I've started a FAQ section of the perldocs. Please look in here before you send me email.

FREQUENTLY ASKED QUESTIONS

Is there a place to go to discuss HTML::Template and/or get help?

There's a mailing-list for discussing HTML::Template at [email protected]. Join at: 

   http://lists.sourceforge.net/lists/listinfo/html-template-users

If you just want to get email when new releases are available you can join the announcements mailing-list here: 

    http://lists.sourceforge.net/lists/listinfo/html-template-announce

Is there a searchable archive for the mailing-list?

Yes, you can find an archive of the SourceForge list here: 

    http://dir.gmane.org/gmane.comp.lang.perl.modules.html-template

I want support for <TMPL_XXX>! How about it?

Maybe. I definitely encourage people to discuss their ideas for HTML::Template on the mailing list. Please be ready to explain to me how the new tag fits in with HTML::Template's mission to provide a fast, lightweight system for using HTML templates.

NOTE: Offering to program said addition and provide it in the form of a patch to the most recent version of HTML::Template will definitely have a softening effect on potential opponents!

I found a bug, can you fix it?

That depends. Did you send me the VERSION of HTML::Template, a test script and a test template? If so, then almost certainly.

If you're feeling really adventurous, HTML::Template is publicly available on GitHub (https://github.com/mpeters/html-template). Please feel free to fork it and send me a pull request with any changes you have.

<TMPL_VAR>s from the main template aren't working inside a <TMPL_LOOP>! Why?

This is the intended behavior. "<TMPL_LOOP>" introduces a separate scope for "<TMPL_VAR>s" much like a subroutine call in Perl introduces a separate scope for "my" variables.

If you want your "<TMPL_VAR>"s to be global you can set the "global_vars" option when you call "new()". See above for documentation of the "global_vars" "new()" option.

How can I pre-load my templates using cache-mode and mod_perl?

Add something like this to your startup.pl: 

    use HTML::Template;
    use File::Find;
    print STDERR "Pre-loading HTML Templates...\n";
    find(
        sub {
            return unless /\.tmpl$/;
            HTML::Template->new(
                filename => "$File::Find::dir/$_",
                cache    => 1,
            );
        },
        '/path/to/templates',
        '/another/path/to/templates/'
    );

Note that you'll need to modify the "return unless" line to specify the extension you use for your template files - I use .tmpl, as you can see. You'll also need to specify the path to your template files.

One potential problem: the /path/to/templates/ must be EXACTLY the same path you use when you call "HTML::Template->new()". Otherwise the cache won't know they're the same file and will load a new copy - instead getting a speed increase, you'll double your memory usage. To find out if this is happening set "cache_debug =" 1> in your application code and look for ``CACHE MISS'' messages in the logs.

What characters are allowed in TMPL_* names?

Numbers, letters, '.', '/', '+', '-' and '_'.

How can I execute a program from inside my template?

Short answer: you can't. Longer answer: you shouldn't since this violates the fundamental concept behind HTML::Template - that design and code should be separate.

But, inevitably some people still want to do it. If that describes you then you should take a look at HTML::Template::Expr. Using HTML::Template::Expr it should be easy to write a "run_program()" function. Then you can do awful stuff like: 

    <tmpl_var expr="run_program('foo.pl')">

Just, please, don't tell me about it. I'm feeling guilty enough just for writing HTML::Template::Expr in the first place.

What's the best way to create a <select> form element using HTML::Template?

There is much disagreement on this issue. My personal preference is to use CGI.pm's excellent "popup_menu()" and "scrolling_list()" functions to fill in a single "<tmpl_var select_foo>" variable.

To some people this smacks of mixing HTML and code in a way that they hoped HTML::Template would help them avoid. To them I'd say that HTML is a violation of the principle of separating design from programming. There's no clear separation between the programmatic elements of the "<form>" tags and the layout of the "<form>" tags. You'll have to draw the line somewhere - clearly the designer can't be entirely in charge of form creation.

It's a balancing act and you have to weigh the pros and cons on each side. It is certainly possible to produce a "<select>" element entirely inside the template. What you end up with is a rat's nest of loops and conditionals. Alternately you can give up a certain amount of flexibility in return for vastly simplifying your templates. I generally choose the latter.

Another option is to investigate HTML::FillInForm which some have reported success using to solve this problem.

LAST SEARCHED