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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 %]?
  - How do I iterate over a hash?
- 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 find out the name of the main template being processed?
  - How can I find out the name of the current template being processed?
  - How do I print the modification time of the template or component?
  - How can I configure variables on a per-request basis?
- AUTHOR
- VERSION
- COPYRIGHT

DESCRIPTION | [ Index ] [ Top ]

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

### 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 | [ 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 <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 | [ 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 find out the name of the main template being processed?

The `'template'` variable contains a reference to the Template::Document object for the main template you're processing (i.e. the one provided as the first argument to the Template process() method). The `'name'` method returns its name.

        [% template.name %]     # e.g. index.html

### How can I find out the name of the current template being processed?

The `'template'` variable always references the main template being processed. So even if you call [% INCLUDE header %], and that calls [% INCLUDE menu %], the `'template'` variable will be unchanged.

index.html:

        [% template.name  %]     # index.html
        [% INCLUDE header %]

header:

        [% template.name  %]     # index.html
        [% INCLUDE menu   %]

menu:

        [% template.name  %]     # index.html

In constrast, the `'component'` variable always references the current template being processed.

index.html

        [% component.name %]     # index.html
        [% INCLUDE header %]

header:

        [% component.name %]     # header
        [% INCLUDE menu   %]

menu:

        [% component.name  %]     # menu

### How do I print the modification time of the template or component?

The `'template'` and `'component'` variables reference the main template and the current template being processed (see previous questions). The `'modtime'` method returns the modification time of the corresponding template file as a number of seconds since the Unix epoch (00:00:00 GMT 1st January 1970).

This number doesn't mean much to anyone (except perhaps serious Unix geeks) so you'll probably want to use the Date plugin to format it for human consumption.

        [% USE Date %]

        [% template.name %] last modified [% Date.format(template.modtime) %]

### 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@wardley.org> http://wardley.org/

VERSION | [ Index ] [ Top ]

2.68, distributed as part of the Template Toolkit version 2.19, released on 27 April 2007.

COPYRIGHT | [ Index ] [ Top ]

      Copyright (C) 1996-2007 Andy Wardley.  All Rights Reserved.

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

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