Andy Wardley > Template-Toolkit-2.00 > Template::Filters

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NAME ^

Template::Filters - post-processing filters for template blocks

SYNOPSIS ^

    use Template::Filters;

    $filters = Template::Filters->new(\%config);

    ($filter, $error) = $filters->fetch($name, \@args, $context);

DESCRIPTION ^

The Template::Plugins module implements a provider for creating and/or returning subroutines that implement the standard filters. Additional custom filters may be provided via the FILTERS options.

METHODS ^

new(\%params)

Constructor method which instantiates and returns a reference to a Template::Filters object. A reference to a hash array of configuration items may be passed as a parameter. These are described below.

    my $filters = Template::Filters->new({
        FILTERS => { ... },
    });

    my $template = Template->new({
        LOAD_FILTERS => [ $filters ],
    });

A default Template::Filters module is created by the Template.pm module if the LOAD_FILTERS option isn't specified. All configuration parameters are forwarded to the constructor.

    $template = Template->new({
        FILTERS => { ... },
    });

fetch($name, \@args, $context)

Called to request that a filter of a given name be provided. The name of the filter should be specified as the first parameter. This should be one of the standard filters or one specified in the FILTERS configuration hash. The second argument should be a reference to an array containing configuration parameters for the filter. This may be specified as 0, or undef where no parameters are provided. The third argument should be a reference to the current Template::Context object.

The method returns a reference to a filter sub-routine on success. It may also return (undef, STATUS_DECLINE) to decline the request, to allow delegation onto other filter providers in the LOAD_FILTERS chain of responsibility. On error, ($error, STATUS_ERROR) is returned where $error is an error message or Template::Exception object indicating the error that occurred.

When the TOLERANT option is set, errors are automatically downgraded to a STATUS_DECLINE response.

CONFIGURATION OPTIONS ^

The following list details the configuration options that can be provided to the Template::Plugins new() constructor.

FILTERS

The FILTERS option can be used to specify custom filters which can then be used with the FILTER directive like any other. These are added to the standard filters which are available by default. Filters specified via this option will mask any standard filters of the same name.

The FILTERS option should be specified as a reference to a hash array in which each key represents the name of a filter. The corresponding value should contain a reference to an array containing a subroutine reference and a flag which indicates if the filter is static (0) or dynamic (1). A filter may also be specified as a solitary subroutine reference and is assumed to be static.

    $filters = Template::Filters->new({
        FILTERS => {
            'sfilt1' =>   \&static_filter,      # static
            'sfilt2' => [ \&static_filter, 0 ], # same as above
            'dfilt1' => [ \&dyanamic_filter_factory, 1 ],
        },
    });

Additional filters can be specified at any time by calling the define_filter() method on the current Template::Context object. The method accepts a filter name, a reference to a filter subroutine and an optional flag to indicate if the filter is dynamic.

    my $context = $template->context();
    $context->define_filter('new_html', \&new_html);
    $context->define_filter('new_repeat', \&new_repeat, 1);

Static filters are those where a single subroutine reference is used for all invocations of a particular filter. Filters that don't accept any configuration parameters (e.g. 'html') can be implemented statically. The subroutine reference is simply returned when that particular filter is requested. The subroutine is called to filter the output of a template block which is passed as the only argument. The subroutine should return the modified text.

    sub static_filter {
        my $text = shift;
        # do something to modify $text...
        return $text;
    }

The following template fragment:

    [% FILTER sfilt1 %]
    Blah blah blah.
    [% END %]

is approximately equivalent to:

    &static_filter("\nBlah blah blah.\n");

Filters that can accept parameters (e.g. 'truncate') should be implemented dynamically. In this case, the subroutine is taken to be a filter 'factory' that is called to create a unique filter subroutine each time one is requested. A reference to the current Template::Context object is passed as the first parameter, followed by any additional parameters specified. The subroutine should return another subroutine reference (usually a closure) which implements the filter.

    sub dynamic_filter_factory {
        my ($context, @args) = @_;

        return sub {
            my $text = shift;
            # do something to modify $text...
            return $text;           
        }
    }

The following template fragment:

    [% FILTER dfilt1(123, 456) %] 
    Blah blah blah
    [% END %]              

is approximately equivalent to:

    my $filter = &dynamic_filter_factory($context, 123, 456);
    &$filter("\nBlah blah blah.\n");

See the FILTER directive for further examples.

TOLERANT

The TOLERANT flag is used by the various Template Toolkit provider modules (Template::Provider, Template::Plugins, Template::Filters) to control their behaviour when errors are encountered. By default, any errors are reported as such, with the request for the particular resource (template, plugin, filter) being denied and an exception raised. When the TOLERANT flag is set to any true values, errors will be silently ignored and the provider will instead return STATUS_DECLINED. This allows a subsequent provider to take responsibility for providing the resource, rather than failing the request outright. If all providers decline to service the request, either through tolerated failure or a genuine disinclination to comply, then a '<resource> not found' exception is raised.

TEMPLATE TOOLKIT FILTERS ^

The following standard filters are distributed with the Template Toolkit.

html

Converts the characters '<', '>' and '&' to '&lt;', '&gt;' and '&amp', respectively, protecting them from being interpreted as representing HTML tags or entities.

    [% FILTER html %]
    Binary "<=>" returns -1, 0, or 1 depending on...
    [% END %]

output:

    Binary "&lt;=&gt;" returns -1, 0, or 1 depending on...
html_para

This filter formats a block of text into HTML paragraphs. A sequence of two or more newlines is used as the delimiter for paragraphs which are then wrapped in HTML <p>...</p> tags.

    [% FILTER html_para %]
    The cat sat on the mat.

    Mary had a little lamb.
    [% END %]

output:

    <p>
    The cat sat on the mat.
    </p>

    <p>
    Mary had a little lamb.
    </p>
html_break

Similar to the html_para filter described above, but uses the HTML tag sequence <br><br> to join paragraphs.

    [% FILTER html_break %]
    The cat sat on the mat.

    Mary had a little lamb.
    [% END %]

output:

    The cat sat on the mat.
    <br>
    <br>
    Mary had a little lamb.
format(format)

The 'format' filter takes a format string as a parameter (as per printf()) and formats each line of text accordingly.

    [% FILTER format('<!-- %-40s -->') %]
    This is a block of text filtered 
    through the above format.
    [% END %]

output:

    <!-- This is a block of text filtered        -->
    <!-- through the above format.               -->
truncate(length)

Truncates the text block to the length specified, or a default length of 32. Truncated text will be terminated with '...' (i.e. the '...' falls inside the required length, rather than appending to it).

    [% FILTER truncate(21) %]
    I have much to say on this matter that has previously 
    been said on more than one occassion.
    [% END %]

output:

    I have much to say...
repeat(iterations)

Repeats the text block for as many iterations as are specified (default: 1).

    [% FILTER repeat(3) %]
    We want more beer and we want more beer,
    [% END %]
    We are the more beer wanters!

output:

    We want more beer and we want more beer,
    We want more beer and we want more beer,
    We want more beer and we want more beer,
    We are the more beer wanters!
remove(string)

Searches the input text for any occurences of the specified string and removes them. A Perl regular expression may be specified as the search string.

    [% "The  cat  sat  on  the  mat" FILTER remove('\s+') %]

output:

    Thecatsatonthemat
replace(search, replace)

Similar to the remove filter described above, but taking a second parameter which is used as a replacement string for instances of the search string.

    [% "The  cat  sat  on  the  mat" | replace('\s+', '_') %]

output:

    The_cat_sat_on_the_mat
redirect(file)

The 'redirect' filter redirects the output of the block into a separate file, specified relative to the OUTPUT_PATH configuration item.

    [% FOREACH user = myorg.userlist %]
       [% FILTER redirect("users/${user.id}.html") %]
          [% INCLUDE userinfo %]
       [% END %]
    [% END %]

or more succinctly, using side-effect notation:

    [% INCLUDE userinfo 
         FILTER redirect("users/${user.id}.html")
           FOREACH user = myorg.userlist 
    %]

A 'file' exception will be thrown if the OUTPUT_PATH option is undefined.

eval(template_text)

The 'eval' filter evaluates the block as template text, processing any directives embedded within it. This allows template variables to contain template fragments, or for some method to be provided for returning template fragments from an external source such as a database, which can then be processed in the template as required.

    my $vars  = {
        fragment => "The cat sat on the [% place %]",
    };
    $template->process($file, $vars);

The following example:

    [% fragment | eval %]

is therefore equivalent to

    The cat sat on the [% place %]

The 'evaltt' filter is provided as an alias for 'eval'.

perl(perlcode)

The 'perl' filter evaluates the block as Perl code. The EVAL_PERL option must be set to a true value or a 'perl' exception will be thrown.

    [% my_perl_code | perl %]

In most cases, the [% PERL %] ... [% END %] block should suffice for evaluating Perl code, given that template directives are processed before being evaluate as Perl. Thus, the previous example could have been written in the more verbose form:

    [% PERL %]
    [% my_perl_code %]
    [% END %]

as well as

    [% FILTER perl %]
    [% my_perl_code %]
    [% END %]

The 'evalperl' filter is provided as an alias for 'perl' for backwards compatability.

stderr

The stderr filter prints the output generating by the enclosing block to STDERR

AUTHOR ^

Andy Wardley <abw@kfs.org>

    http://www.template-toolkit.org/
    http://www.kfs.org/~abw/

REVISION ^

$Revision: 1.1 $

COPYRIGHT ^

    Copyright (C) 1996-2000 Andy Wardley.  All Rights Reserved.
    Copyright (C) 1998-2000 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.

SEE ALSO ^

Template, Template::Context

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