FREQUENTLY ASKED QUESTIONS
In the interest of greater understanding I've started a FAQ section of
the perldocs. Please look in here before you send me email.
1 Q: Is there a place to go to discuss HTML::Template and/or get help?
A: There's a mailing-list for discussing HTML::Template at
html-template-users@lists.sourceforge.net. To join:
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
2 Q: Is there a searchable archive for the mailing-list?
A: Yes, you can find an archive of the SourceForge list here:
http://www.geocrawler.com/lists/3/SourceForge/23294/0/
For an archive of the old vm.com list, setup by Sean P. Scanlon,
see:
http://bluedot.net/mail/archive/
3 Q: I want support for <TMPL_XXX>! How about it?
A: 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!
4 Q: I found a bug, can you fix it?
A: 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 has a
publically available CVS server. See below for more information in
the PUBLIC CVS SERVER section.
5 Q: <TMPL_VAR>s from the main template aren't working inside a
<TMPL_LOOP>! Why?
A: 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.
6 Q: Why do you use /[Tt]/ instead of /t/i? It's so ugly!
A: Simple - the case-insensitive match switch is very inefficient.
According to _Mastering_Regular_Expressions_ from O'Reilly Press,
/[Tt]/ is faster and more space efficient than /t/i - by as much as
double against long strings. //i essentially does a lc() on the
string and keeps a temporary copy in memory.
When this changes, and it is in the 5.6 development series, I will
gladly use //i. Believe me, I realize [Tt] is hideously ugly.
7 Q: How can I pre-load my templates using cache-mode and mod_perl?
A: 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.
8 Q: What characters are allowed in TMPL_* NAMEs?
A: Numbers, letters, '.', '/', '+', '-' and '_'.
9 Q: How can I execute a program from inside my template?
A: 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 seperate.
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.
10 Q: Can I get a copy of these docs in Japanese?
A: Yes you can. See Kawai Takanori's translation at:
http://member.nifty.ne.jp/hippo2000/perltips/html/template.htm
11 Q: What's the best way to create a <select> form element using
HTML::Template?
A: 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.