1Template::Filters(3) User Contributed Perl Documentation Template::Filters(3)
2
6 Template::Filters - Post-processing filters for template blocks
7
9 use Template::Filters;
10 $filters = Template::Filters->new(\%config);
12 ($filter, $error) = $filters->fetch($name, \@args, $context);
14
16 The Template::Filters module implements a provider for creating and/or
17 returning subroutines that implement the standard filters. Additional
18 custom filters may be provided via the FILTERS options.
19
21 new(\%params)
22 Constructor method which instantiates and returns a reference to a Tem‐
24 plate::Filters object. A reference to a hash array of configuration
25 items may be passed as a parameter. These are described below.
26 my $filters = Template::Filters->new({
28 FILTERS => { ... },
29 });
30 my $template = Template->new({
32 LOAD_FILTERS => [ $filters ],
33 });
34 A default Template::Filters module is created by the Template.pm module
36 if the LOAD_FILTERS option isn't specified. All configuration parame‐
37 ters are forwarded to the constructor.
38 $template = Template->new({
40 FILTERS => { ... },
41 });
42 fetch($name, \@args, $context)
44 Called to request that a filter of a given name be provided. The name
46 of the filter should be specified as the first parameter. This should
47 be one of the standard filters or one specified in the FILTERS configu‐
48 ration hash. The second argument should be a reference to an array
49 containing configuration parameters for the filter. This may be speci‐
50 fied as 0, or undef where no parameters are provided. The third argu‐
51 ment should be a reference to the current Template::Context object.
52 The method returns a reference to a filter sub-routine on success. It
54 may also return (undef, STATUS_DECLINE) to decline the request, to
55 allow delegation onto other filter providers in the LOAD_FILTERS chain
56 of responsibility. On error, ($error, STATUS_ERROR) is returned where
57 $error is an error message or Template::Exception object indicating the
58 error that occurred.
59 When the TOLERANT option is set, errors are automatically downgraded to
61 a STATUS_DECLINE response.
62
64 The following list details the configuration options that can be pro‐
65 vided to the Template::Filters new() constructor.
66 FILTERS
68 The FILTERS option can be used to specify custom filters which can
69 then be used with the FILTER directive like any other. These are
70 added to the standard filters which are available by default. Fil‐
71 ters specified via this option will mask any standard filters of
72 the same name.
73 The FILTERS option should be specified as a reference to a hash
75 array in which each key represents the name of a filter. The cor‐
76 responding value should contain a reference to an array containing
77 a subroutine reference and a flag which indicates if the filter is
78 static (0) or dynamic (1). A filter may also be specified as a
79 solitary subroutine reference and is assumed to be static.
80 $filters = Template::Filters->new({
82 FILTERS => {
83 'sfilt1' => \&static_filter, # static
84 'sfilt2' => [ \&static_filter, 0 ], # same as above
85 'dfilt1' => [ \&dyanamic_filter_factory, 1 ],
86 },
87 });
88 Additional filters can be specified at any time by calling the
90 define_filter() method on the current Template::Context object.
91 The method accepts a filter name, a reference to a filter subrou‐
92 tine and an optional flag to indicate if the filter is dynamic.
93 my $context = $template->context();
95 $context->define_filter('new_html', \&new_html);
96 $context->define_filter('new_repeat', \&new_repeat, 1);
97 Static filters are those where a single subroutine reference is
99 used for all invocations of a particular filter. Filters that
100 don't accept any configuration parameters (e.g. 'html') can be
101 implemented statically. The subroutine reference is simply
102 returned when that particular filter is requested. The subroutine
103 is called to filter the output of a template block which is passed
104 as the only argument. The subroutine should return the modified
105 text.
106 sub static_filter {
108 my $text = shift;
109 # do something to modify $text...
110 return $text;
111 }
112 The following template fragment:
114 [% FILTER sfilt1 %]
116 Blah blah blah.
117 [% END %]
118 is approximately equivalent to:
120 &static_filter("\nBlah blah blah.\n");
122 Filters that can accept parameters (e.g. 'truncate') should be
124 implemented dynamically. In this case, the subroutine is taken to
125 be a filter 'factory' that is called to create a unique filter sub‐
126 routine each time one is requested. A reference to the current
127 Template::Context object is passed as the first parameter, followed
128 by any additional parameters specified. The subroutine should
129 return another subroutine reference (usually a closure) which
130 implements the filter.
131 sub dynamic_filter_factory {
133 my ($context, @args) = @_;
134 return sub {
136 my $text = shift;
137 # do something to modify $text...
138 return $text;
139 }
140 }
141 The following template fragment:
143 [% FILTER dfilt1(123, 456) %]
145 Blah blah blah
146 [% END %]
147 is approximately equivalent to:
149 my $filter = &dynamic_filter_factory($context, 123, 456);
151 &$filter("\nBlah blah blah.\n");
152 See the FILTER directive for further examples.
154 TOLERANT
156 The TOLERANT flag is used by the various Template Toolkit provider
157 modules (Template::Provider, Template::Plugins, Template::Filters)
158 to control their behaviour when errors are encountered. By
159 default, any errors are reported as such, with the request for the
160 particular resource (template, plugin, filter) being denied and an
161 exception raised. When the TOLERANT flag is set to any true val‐
162 ues, errors will be silently ignored and the provider will instead
163 return STATUS_DECLINED. This allows a subsequent provider to take
164 responsibility for providing the resource, rather than failing the
165 request outright. If all providers decline to service the request,
166 either through tolerated failure or a genuine disinclination to
167 comply, then a '<resource> not found' exception is raised.
168 DEBUG
170 The DEBUG option can be used to enable debugging messages from the
171 Template::Filters module by setting it to include the DEBUG_FILTERS
172 value.
173 use Template::Constants qw( :debug );
175 my $template = Template->new({
177 DEBUG => DEBUG_FILTERS ⎪ DEBUG_PLUGINS,
178 });
179
181 The following standard filters are distributed with the Template Tool‐
182 kit.
183 format(format)
185 The 'format' filter takes a format string as a parameter (as per
187 printf()) and formats each line of text accordingly.
188 [% FILTER format('<!-- %-40s -->') %]
190 This is a block of text filtered
191 through the above format.
192 [% END %]
193 output:
195 <!-- This is a block of text filtered -->
197 <!-- through the above format. -->
198 upper
200 Folds the input to UPPER CASE.
202 [% "hello world" FILTER upper %]
204 output:
206 HELLO WORLD
208 lower
210 Folds the input to lower case.
212 [% "Hello World" FILTER lower %]
214 output:
216 hello world
218 ucfirst
220 Folds the first character of the input to UPPER CASE.
222 [% "hello" FILTER ucfirst %]
224 output:
226 Hello
228 lcfirst
230 Folds the first character of the input to lower case.
232 [% "HELLO" FILTER lcfirst %]
234 output:
236 hELLO
238 trim
240 Trims any leading or trailing whitespace from the input text. Particu‐
242 larly useful in conjunction with INCLUDE, PROCESS, etc., having the
243 same effect as the TRIM configuration option.
244 [% INCLUDE myfile ⎪ trim %]
246 collapse
248 Collapse any whitespace sequences in the input text into a single
250 space. Leading and trailing whitespace (which would be reduced to a
251 single space) is removed, as per trim.
252 [% FILTER collapse %]
254 The cat
256 sat on
258 the mat
260 [% END %]
262 output:
264 The cat sat on the mat
266 html
268 Converts the characters '<', '>', '&' and '"' to '<', '>',
270 '&', and '"' respectively, protecting them from being inter‐
271 preted as representing HTML tags or entities.
272 [% FILTER html %]
274 Binary "<=>" returns -1, 0, or 1 depending on...
275 [% END %]
276 output:
278 Binary "<=>" returns -1, 0, or 1 depending on...
280 html_entity
282 The html filter is fast and simple but it doesn't encode the full range
284 of HTML entities that your text may contain. The html_entity filter
285 uses either the Apache::Util module (which is written in C and is
286 therefore faster) or the HTML::Entities module (written in Perl but
287 equally as comprehensive) to perform the encoding. If one or other of
288 these modules are installed on your system then the text will be
289 encoded (via the escape_html() or encode_entities() subroutines respec‐
290 tively) to convert all extended characters into their appropriate HTML
291 entities (e.g. converting 'é' to 'é'). If neither module is
292 available on your system then an 'html_entity' exception will be thrown
293 reporting an appropriate message.
294 For further information on HTML entity encoding, see
296 http://www.w3.org/TR/REC-html40/sgml/entities.html.
297 html_para
299 This filter formats a block of text into HTML paragraphs. A sequence
301 of two or more newlines is used as the delimiter for paragraphs which
302 are then wrapped in HTML <p>...</p> tags.
303 [% FILTER html_para %]
305 The cat sat on the mat.
306 Mary had a little lamb.
308 [% END %]
309 output:
311 <p>
313 The cat sat on the mat.
314 </p>
315 <p>
317 Mary had a little lamb.
318 </p>
319 html_break / html_para_break
321 Similar to the html_para filter described above, but uses the HTML tag
323 sequence <br><br> to join paragraphs.
324 [% FILTER html_break %]
326 The cat sat on the mat.
327 Mary had a little lamb.
329 [% END %]
330 output:
332 The cat sat on the mat.
334 <br>
335 <br>
336 Mary had a little lamb.
337 html_line_break
339 This filter replaces any newlines with <br> HTML tags, thus preserving
341 the line breaks of the original text in the HTML output.
342 [% FILTER html_line_break %]
344 The cat sat on the mat.
345 Mary had a little lamb.
346 [% END %]
347 output:
349 The cat sat on the mat.<br>
351 Mary had a little lamb.<br>
352 uri
354 This filter URI escapes the input text, converting any characters out‐
356 side of the permitted URI character set (as defined by RFC 2396) into a
357 %nn hex escape.
358 [% 'my file.html' ⎪ uri %]
360 output:
362 my%20file.html
364 Note that as of TT version 2.16, the uri filter now correctly encodes
366 all reserved characters. This includes "&", "@", "/", ";", ":", "=",
367 "+", "?" and "$" which were not escaped (incorrectly) by the uri filter
368 in versions 2.15 and earlier. See RFC 2396 for further details.
369 indent(pad)
371 Indents the text block by a fixed pad string or width. The 'pad' argu‐
373 ment can be specified as a string, or as a numerical value to indicate
374 a pad width (spaces). Defaults to 4 spaces if unspecified.
375 [% FILTER indent('ME> ') %]
377 blah blah blah
378 cabbages, rhubard, onions
379 [% END %]
380 output:
382 ME> blah blah blah
384 ME> cabbages, rhubard, onions
385 truncate(length,dots)
387 Truncates the text block to the length specified, or a default length
389 of 32. Truncated text will be terminated with '...' (i.e. the '...'
390 falls inside the required length, rather than appending to it).
391 [% FILTER truncate(21) %]
393 I have much to say on this matter that has previously
394 been said on more than one occasion.
395 [% END %]
396 output:
398 I have much to say...
400 If you want to use something other than '...' you can pass that as a
402 second argument.
403 [% FILTER truncate(26, '…') %]
405 I have much to say on this matter that has previously
406 been said on more than one occasion.
407 [% END %]
408 output:
410 I have much to say…
412 repeat(iterations)
414 Repeats the text block for as many iterations as are specified
416 (default: 1).
417 [% FILTER repeat(3) %]
419 We want more beer and we want more beer,
420 [% END %]
421 We are the more beer wanters!
422 output:
424 We want more beer and we want more beer,
426 We want more beer and we want more beer,
427 We want more beer and we want more beer,
428 We are the more beer wanters!
429 remove(string)
431 Searches the input text for any occurrences of the specified string and
433 removes them. A Perl regular expression may be specified as the search
434 string.
435 [% "The cat sat on the mat" FILTER remove('\s+') %]
437 output:
439 Thecatsatonthemat
441 replace(search, replace)
443 Similar to the remove filter described above, but taking a second
445 parameter which is used as a replacement string for instances of the
446 search string.
447 [% "The cat sat on the mat" ⎪ replace('\s+', '_') %]
449 output:
451 The_cat_sat_on_the_mat
453 redirect(file, options)
455 The 'redirect' filter redirects the output of the block into a separate
457 file, specified relative to the OUTPUT_PATH configuration item.
458 [% FOREACH user = myorg.userlist %]
460 [% FILTER redirect("users/${user.id}.html") %]
461 [% INCLUDE userinfo %]
462 [% END %]
463 [% END %]
464 or more succinctly, using side-effect notation:
466 [% INCLUDE userinfo
468 FILTER redirect("users/${user.id}.html")
469 FOREACH user = myorg.userlist
470 %]
471 A 'file' exception will be thrown if the OUTPUT_PATH option is unde‐
473 fined.
474 An optional 'binmode' argument can follow the filename to explicitly
476 set the output file to binary mode.
477 [% PROCESS my/png/generator
479 FILTER redirect("images/logo.png", binmode=1) %]
480 For backwards compatibility with earlier versions, a single true/false
482 value can be used to set binary mode.
483 [% PROCESS my/png/generator
485 FILTER redirect("images/logo.png", 1) %]
486 For the sake of future compatibility and clarity, if nothing else, we
488 would strongly recommend you explicitly use the named 'binmode' option
489 as shown in the first example.
490 eval / evaltt
492 The 'eval' filter evaluates the block as template text, processing any
494 directives embedded within it. This allows template variables to con‐
495 tain template fragments, or for some method to be provided for return‐
496 ing template fragments from an external source such as a database,
497 which can then be processed in the template as required.
498 my $vars = {
500 fragment => "The cat sat on the [% place %]",
501 };
502 $template->process($file, $vars);
503 The following example:
505 [% fragment ⎪ eval %]
507 is therefore equivalent to
509 The cat sat on the [% place %]
511 The 'evaltt' filter is provided as an alias for 'eval'.
513 perl / evalperl
515 The 'perl' filter evaluates the block as Perl code. The EVAL_PERL
517 option must be set to a true value or a 'perl' exception will be
518 thrown.
519 [% my_perl_code ⎪ perl %]
521 In most cases, the [% PERL %] ... [% END %] block should suffice for
523 evaluating Perl code, given that template directives are processed
524 before being evaluate as Perl. Thus, the previous example could have
525 been written in the more verbose form:
526 [% PERL %]
528 [% my_perl_code %]
529 [% END %]
530 as well as
532 [% FILTER perl %]
534 [% my_perl_code %]
535 [% END %]
536 The 'evalperl' filter is provided as an alias for 'perl' for backwards
538 compatibility.
539 stdout(options)
541 The stdout filter prints the output generated by the enclosing block to
543 STDOUT. The 'binmode' option can be passed as either a named parameter
544 or a single argument to set STDOUT to binary mode (see the binmode perl
545 function).
546 [% PROCESS something/cool
548 FILTER stdout(binmode=1) # recommended %]
549 [% PROCESS something/cool
551 FILTER stdout(1) # alternate %]
552 The stdout filter can be used to force binmode on STDOUT, or also
554 inside redirect, null or stderr blocks to make sure that particular
555 output goes to stdout. See the null filter below for an example.
556 stderr
558 The stderr filter prints the output generated by the enclosing block to
560 STDERR.
561 null
563 The null filter prints nothing. This is useful for plugins whose meth‐
565 ods return values that you don't want to appear in the output. Rather
566 than assigning every plugin method call to a dummy variable to silence
567 it, you can wrap the block in a null filter:
568 [% FILTER null;
570 USE im = GD.Image(100,100);
571 black = im.colorAllocate(0, 0, 0);
572 red = im.colorAllocate(255,0, 0);
573 blue = im.colorAllocate(0, 0, 255);
574 im.arc(50,50,95,75,0,360,blue);
575 im.fill(50,50,red);
576 im.png ⎪ stdout(1);
577 END;
578 -%]
579 Notice the use of the stdout filter to ensure that a particular expres‐
581 sion generates output to stdout (in this case in binary mode).
582 latex(outputType)
584 The latex() filter is no longer part of the core Template Toolkit dis‐
586 tribution as of version 2.15. You can download it as a separate Tem‐
587 plate-Latex distribution from CPAN.
588
590 Andy Wardley <abw@wardley.org>
591 <http://wardley.org/⎪http://wardley.org/>
593
595 2.85, distributed as part of the Template Toolkit version 2.18,
596 released on 09 February 2007.
597
599 Copyright (C) 1996-2007 Andy Wardley. All Rights Reserved.
600 This module is free software; you can redistribute it and/or modify it
602 under the same terms as Perl itself.
603
605 Template, Template::Context, Template::Manual::Filters
606perl v5.8.8 2007-02-09 Template::Filters(3)