Template::FAQ(3)

NAME
Template::FAQ - Frequently Asked Questions about the Template Toolkit

DESCRIPTION
This is the Frequently Asked Questions list for the Template Toolkit. More accurately, it's a very thin placeholder for where the FAQ will soon be.

Template Toolkit Language

  Why doesn't [% a = b IF c %] work as expected?
Because the parser interprets it as

    [% a = (b IF c) %]

Do this instead:

    [% SET a = b IF c %]

  If I'm using TT to write out a TT template, is there a good way to escape [% and %]?
You can do this:

  [% stag = "[\%"
     etag = "%\]"
  %]

and then:

  [% stag; 'hello'; etag %]

Or something like:

  [% TAGS [- -] %]
  [- INCLUDE foo -]   # is a directive
  [% INCLUDE foo %]   # not a directive, just plain text, passed through

  How do I iterate over a hash?
This is covered in the Template::Manual::VMethods section of the manual page. A list of all the keys that are in the hash can be obtained with the 'keys' virtual method. You can then iterate over that list and by looking up each key in turn get the value.

    [% FOREACH key = product.keys %]
       [% key %] => [% product.$key %]
    [% END %]

Plugins

  How do I get the Table plugin to order data across rather than down?
Order the data into rows:

     Steve     Karen     Jeff
     Brooklyn  Nantucket Fairfax
     NY        MA        VA

    [% USE table(data, rows=3) %]

Then ask for each column

    [% FOREACH column = table.cols %]

And then print each item in the column going across the output rows

    [% FOREACH item = column %]
        <td>[% item %]</td>
    [% END %]

  Accessing Cookies
Jeff Boes <jboes@nexcerpt.com> asks:

    Does anyone have a quick-n-dirty approach to accessing
    cookies from templates?

Jonas Liljegren answers:

    [% USE CGI %]

    <p>The value is [% CGI.cookie('cookie_name') | html %]

Extending the Template Toolkit

  Can I serve templates from a database?
Short answer: yes, Chris Nandor has done this for Slash. You need to subclass Template::Provider. See the mailing list archives for further info.

  Can I fetch templates via http?
To do the job properly, you should sublcass Template::Provider to Template::Provider::HTTP and use a PREFIX_MAP option to bind the 'http' template prefix to that particular provider (you may want to go digging around in the Changes file around version 2.01 for more info on PREFIX_MAP - it may not be properly documented anywhere else...yet!). e.g. (untested due to lack of existing HTTP Provider - patches welcome!).

    use Template::Provider::HTTP;

    my $file = Template::Provider( INCLUDE_PATH => [...] );
    my $http = Template::Provider::HTTP->new(...);
    my $tt2  = Template->new({
        LOAD_TEMPLATES => [ $file, $http ],
        PREFIX_MAP => {
            file    => '0',     # file:foo.html
            http    => '1',     # http:foo.html
            default => '0',     # foo.html => file:foo.html
        }
    });

Now a template specified as:

    [% INCLUDE foo %]

will be served by the 'file' provider (the default). Otherwise you can explicitly add a prefix:

    [% INCLUDE file:foo.html %]
    [% INCLUDE http:foo.html %]
    [% INCLUDE http://www.xyz.com/tt2/header.tt2 %]

This same principal can be used to create a DBI template provider. e.g.

    [% INCLUDE dbi:foo.html %]

But similarly, alas, we don't yet have a DBI provider as part of the Template Toolkit. There has been some talk on the mailing list about efforts to develop DBI and/or HTTP providers but as yet no-one has stepped forward to take up the challenge...

In the mean time, Craig's post from the mailing list has some useful pointers on how to acheive this using existing modules:

    To: Adam Theo <adamtheo@theoretic.com>
    From: Craig Barratt <craig@arraycomm.com>
    Date: Fri, 18 May 2001 17:06:59 -0700

    > i was wondering if there is anyway to fetch a file using http:// or
    > ftp:// and include that?

    Here's one way.  Set the LOAD_PERL option:

        use Template;

        my $template = Template->new({
            LOAD_PERL => 1
        });
        $template->process("example.tt", { stdout => *STDOUT })
                                     || die $template->error();

    and then use LWP::UserAgent and HTTP::Request:

        [%
            USE ua = LWP.UserAgent;
            ua.proxy("http", "http://your_proxy/");
            USE req = HTTP.Request("GET", "http://www.cpan.org");
            ua.request(req).content;
        -%]

    For FTP use Net::FTP:

        [%
            USE ftp = Net.FTP("ftp.cpan.org");
            x = ftp.login("anonymous", "me@here.there");
            x = ftp.cwd("/");
            x = ftp.get("welcome.msg", stdout);
            x = ftp.quit;
        -%]

    Normally ftp.get would write the file into the current directory.
    Instead we pass stdout as a second argument so that it is written
    to stdout.  We set stdout to STDOUT in the variables we pass to
    process.

    Craig

Miscellaneous

  How can I configure variables on a per-request basis?
One easy way to acheive this is to define a single PRE_PROCESS template which loads in other configuration files based on variables defined or other conditions.

For example, my setup usually looks something like this:

    PRE_PROCESS => 'config/main'

config/main:

    [%  DEFAULT  style   = 'text'
                 section =  template.section or 'home';

        PROCESS  config/site
              +  config/urls
              +  config/macros
              + "config/style/$style"
              + "config/section/$section"
              + ...
    %]

This allows me to set a single 'style' variable to control which config file gets pre-processed to set my various style options (colours, img paths, etc). For example:

config/style/basic:

    [%  style = {
            name = style    # save existing 'style' var as 'style.name'

            # define various other style variables....
            col = {
                back => '#ffffff'
                text => '#000000'
                # ...etc...
            }

            logo = {
                # ...etc...
            }

            # ...etc...
        }
    %]

Each source template can declare which section it's in via a META directive:

  [% META
       title   = 'General Information'
       section = 'info'
  %]

  ...

This controls which section configuration file gets loaded to set various other variables for defining the section title, menu, etc.

config/section/info:

    [%  section = {
            name   = section  # save 'section' var as 'section.name'
            title  = 'Information'
            menu   = [ ... ]
            # ...etc...
        }
    %]

This illustrates the basic principal but you can extend it to perform pretty much any kind of per-document initialisation that you require.

AUTHOR
Andy Wardley <abw@andywardley.com>

<http://www.andywardley.com/|http://www.andywardley.com/>

VERSION
2.70, distributed as part of the Template Toolkit version 2.14, released on 04 October 2004.

COPYRIGHT
  Copyright (C) 1996-2004 Andy Wardley.  All Rights Reserved.
  Copyright (C) 1998-2002 Canon Research Centre Europe Ltd.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.