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| Template Toolkit | FAQ | Frequently Asked Questions |

## Frequently Asked Questions

Frequently Asked Questions about the Template Toolkit

### Table of Contents

- DESCRIPTION
- Template Toolkit Language
  - Why doesn't [% a = b IF c %] work as expected?
  - If I'm using TT to write out a TT template, is there a good way to escape [% and %]?
- Plugins
  - How do I get the Table plugin to order data across rather than down?
  - Accessing Cookies
- Extending the Template Toolkit
  - Can I serve templates from a database?
  - Can I fetch templates via http?
- Miscellaneous
  - How can I configure variables on a per-request basis?
- AUTHOR
- VERSION
- COPYRIGHT

DESCRIPTION | [ Index ] [ Top ]

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 | [ Index ] [ Top ]

### 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

Plugins | [ Index ] [ Top ]

### 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 <boes@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 | [ Index ] [ Top ]

### 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 <file>Changes</file> 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 | [ Index ] [ Top ]

### 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 | [ Index ] [ Top ]

Andy Wardley <abw@andywardley.com> http://www.andywardley.com/

VERSION | [ Index ] [ Top ]

2.54, distributed as part of the Template Toolkit version 2.08, released on 30 July 2002.

COPYRIGHT | [ Index ] [ Top ]

      Copyright (C) 1996-2002 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.

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