NAME

TX - a simple template system based on Text::Template::Library

SYNOPSIS

use TX;
my $T=TX->new( delimiters=>[qw/<% %>/],
               path=>[qw!/path/to/dir1 /path/to/dir2 ...!],
               binmode=>':utf8',             # how to read template files
               cachesize=>$max_cached_templates,
               evalcache=>\%another_hash,
               evalcachesize=>$max_items_in_another_hash,
               export_include=>0,            # default is 1
               auto_reload_templates=>1,     # default is 0
               prepend=>'use warnings',      # default not set
               output=>sub {...},            # default undef
               package=>'My::Dummy',         # default TX::__
               );

$T->include( 'template1', key=>'value', ...);
$T->include( 'template1', {OUTPUT=>'', ...}, key=>'value', ...);

use TX qw/include/;

@ENV{qw/TEMPLATE_PATH TEMPLATE_BINMODE
        TEMPLATE_DELIMITERS TEMPLATE_EVALCACHE/}=
  ('/path/to/dir1:/path/to/dir2', ':utf8', "<%\t%>", 1);

include( 'template1', {OUTPUT=>'', ...}, key=>'value', ...);

template1.tmpl may contain:

<% define mymacro %>
...
<% /define %>

call macro defined in the same template:
  <% include '#mymacro', key=>'value', ... %>

call macro defined somewhere else:
  <% include 'library#libmacro1', key=>'value', ... %>

library.tmpl may contain:

<% define libmacro1 %>
...
<% /define %>

<% define libmacro2 %>
...
<% /define %>

DESCRIPTION

Text::Template::Base and Text::Template::Library are good at processing single templates. They lack the ability to manage sets of template files. This module adds that functionality in a (what I think) user friendly manner.

The most important function of this module is include. It actually processes the template. include can be called in 2 ways, as simple subroutine or as object method. The second way introduces much more features and hence should be prefered. If called as simple subroutine an internal object is created and and initialized from environment variables.

The object oriented interface

All keys passed to the constructor new are also usable as accessor methods, e.g. $object->output=sub {...};. They methods can be used as Lvalues.

TX->new(key=>value, ...)

creates a TX object. Options are passed as key, value pairs.

delimiters

Specify delimiters used in the templates. If omitted the environment variable TEMPLATE_DELIMITERS is used.

The value can be an array that contains 2 strings or a string. In the latter case the string is splitted into 2 by the tabulator \t+ character. If that fails \s+ is tried. If one of them produces a 2 element list it is used as delimiters.

Example:

Those 3 are equivalent:
```
delimiters => [qw/<% %>/]
delimiters => "<%\t%>"
delimiters => "<% %>"
```
as are those 2 (note the additional space characters):
```
delimiters => ['<% ', ' %>']
delimiters => "<% \t %>"
```
but those are not:
```
delimiters => ['<% ', ' %>']
delimiters => "<%  %>"
```
path

Specify a search path where to look for templates. The format corresponds to that used for the PATH variable on your system. If omitted the environment variable TEMPLATE_PATH is used.

As value is expected either an array or a string. In the latter case it is split up by your local path separator (see "path_sep" in Config).

Template files are searched in the order given by the path. Additionally to each template name the file name extensions .tmpl and .html are appended while looking for it in a given directory.

So, assume dir1:dir2 is passed as path and the file dir2/template.tmpl exists. The the call
```
include 'template', ...
```
will try dir1/template, dir1/template.tmpl, dir1/template.html, dir2/template and then find dir2/template.tmpl.
binmode

Specify a perlio layer to read template files. If omitted the environment variable TEMPLATE_BINMODE is used.

If your templates use UTF8 encoding pass utf8 or :utf8 here.
cachesize

A TX object maintains a template cache to hold compiled templates and thus to avoid reading them from disk each time. Internally it is implemented as a hash with the template names as key. You can access that cache via $object->cache.

If a cache size greater than zero is given the hash is tied to Tie::Cache::LRU to limit the number of cached templates.
auto_reload_templates

If set to true TX tracks whether a cached template has changed after the most recent read. For best performance try to avoid that feature.
evalcache and evalcachesize

This cache corresponds to the EVALCACHE parameter of Text::Template::Base objects. If evalcachesize greater than zero is given it is tied to Tie::Cache::LRU to limit the number of cached compiled code fragments.

The value passed as evalcache can be either a hash reference or a boolean. In the latter case an anonymous hash is created if a true value is passed.
prepend

Almost corresponds to the Text::Template::Base PREPEND parameter. At template compile time the string
```
use strict; our (%V, %G, %L);
```
is appended to the current value. That means code fragments are always evaluated in strict mode and the hashes %V, %G and %L are declared.
output

Corresponds more or less to the Text::Template::Base OUTPUT parameter.

If omitted \*STDOUT is used. So by default the output is directly sent to STDOUT. If a scalar is assigned the output is returned as a string result from include. Also a function can be set. In that case each time a piece of output is ready that function is called with the data is passed as $_[0].

The value specified here is only the default value. It can be overridden by the %options parameter to include.
package

Corresponds to the Text::Template::Base PACKAGE parameter. If omitted TX::__ is used. Code fragments in templates are evaluated in this package.

The value specified here is only the default value. It can be overridden by the %options parameter to include.
export_include

This boolean value specifies whether or not to export the include function into the package given by the package parameter or the package passed in the %options hash to include. If true the template author can call
```
include ...
```
otherwise it is necessary to use the fully specified name:
```
TX::include ...
```
This option is true by default.
preserve_G

If set to a true value $template-G> is not initialized as an empty hash on the toplevel include() invocation.

$object->include($template, \%options, key=>value, ...)

This method processes the template $template. The template may be given as a filename or the basename of a filename (filename without extension) or as a hash reference.

In the former case the template is looked up in the template search path unless it is already present in the template cache.

If a hash is passed in as template it is expected to have at least the following entries, template - the template string (that would be otherwise read from the template file) and filename - a name under which the template can be cached. Make sure to use file names that may not occur in your operating system, e.g. names starting with a \0 character.

Data is passed to the template as key, value pairs after the optional \%options parameter. These parameters are collected into a hash and made accessible inside the template as %V. So, a value passed by a certain KEY is accessed from the template as $V{KEY}.

Further, the 2 hashes %L and %G are available to pass data around. %G is a global hash in a certain meaning. Normally, it is initialized as an empty hash by the outermost include call, the one that is invoked from your perl program in contrast to invocations from within templates. All templates and template modules share the same %G. When the outermost include call is done it is accessible as %{$object->G}. So if you carry around large data structures, open filehandles or similar that may cause undesireable side effects consider to undef it after the call:

$template->include(...);
undef $template->G;            # G is an lvalue function

As said before %G is normally initialized as an empty hash. But suppose there is a set of templates that somehow belong together and want to carry around data between toplevel calls. %G is not usable in this case. But if the preserve_G object property is set and $template->G is set to a hash reference before the outermost call %G will not be reset as in:

$template->G=\my %G;
$G{'meaning of life'}=42;
$template->preserve_G=1;
$template->include(...);
# $G{'meaning of life'} is still 42 if not
# overwritten by the template

This way it can be used to pass data in and out of a template and to carry data around between toplevel include calls.

%L is sort of local. Each time include is called a new %L hash is created. For example:

[% define m1 %]
  G=[% ++$G{g} %] L=[% ++$L{l} %]
[% /define %]

[% $G{g}=10; $L{l}=10; '' #init some hash members %]

[% ++$G{g}         # will output 11 %]
[% ++$L{l}         # will output 11 %]
[% include '#m1'   # will output G=12 L=1 (a localized %L is used) %]
[% ++$G{g}         # will output 13 %]
[% ++$L{l}         # will output 12 %]

Code fragments are evaluated with use strict in effect. The 3 hashes %V, %G and %L are declared with the our keyword.

The optional \%options hash reference is used to modify the current include operation. You can

override the default output destination. For example $object->output is set to a file handle. In a template you want to include the output of another one but postprocess the string a bit. Then you can do:
```
my $string=include $template, {OUTPUT=>''}, ...;
$string=~s/(\w+)/ucfirst $1/ge;
OUT $string;
```
This makes sure that $string really receives the output of the template evaluation no matter that the objects output destination is set to a file handle.
override the evaluation package. Normally you'll set the evaluation package as an object property or use the default package TX::__. Sometimes it may be handy to evaluate certain templates in another package. Be aware that Text::Template::Base installs a $OUT variable and a OUT function in that package. If $object->export_include is set (the default) this module installs a include function in the package.
modify the way the parameters are merged into the %V hash. Normally a local()ized version containing only the currently passed parameters is created.

The VMODE option is used to modify that behavior. It is intended to be used inside a template, not at top level.
- keep
  
  The current %V hash is passed to the template. The remaining parameter list is ignored. In this mode the callee can modify the caller's %V.
- add
  
  A new %V is created as a clone from the caller's %V. Then the parameter list is incorporated into the new hash adding thus new keys and overriding existing ones.

In case of an error include throws an exception. If the error occures in a template the template file name and line number are given along with the error message. If a template throws an error object or any other reference it is propagated unchanged.

$object->G

returns \%G after a call to include.

$object->clear_cache

$object->clear_cache($string_or_regexp, $delete)

$object->clear_cache($string)

Clears the template cache. If called without parameters the whole cache is cleared.

If 2 parameters are given the first is interpreted as regexp. It may be a string containing a regexp or a Regexp object (the result of a qr/.../). If the second parameter is true all matching cache elements are dropped otherwise all non-matching. That means in the latter case matching cache elements are preserved.

If only one parameter is given and it is a Regexp object all non-matching cache elements are dropped.

If only one parameter is given and it is a string the first character of the string value decides if the matching or non-matching cache elements are to be removed. If it is a exclamation mark (!) it is deleted from the string. Then the string is interpreted as regular expression and all matching cache elements are dropped. Otherwise the whole string (including the first character) is interpreted as regular expression and all non-matching cache elements are dropped.

Functional Interface

If include is called without the first parameter being a TX object or subclassed object of TX the default object $TX::TX is used. $TX::TX is initialized at the first call according to the environment variables as explained above.

SUBCLASSING

TX is internally represented a an array. The first few elements are used to hold its properties. @TX::attributes holds a list of property names. If a subclass wants to add new properties it must not override the existing ones. So, new attributes can be added this way:

  package My::TX;

  use strict;
  use warnings;

  use TX;
  @My::TX::ISA=qw/TX/;

  our @attributes;
  BEGIN {
    # define attributes and implement accessor methods
    @attributes=(TX::attributes(), qw/p1 p2 _p3/);
    for( my $i=TX::attributes(); $i<@attributes; $i++ ) {
      my $method_num=$i;
      ## no critic
      no strict 'refs';
      *{__PACKAGE__.'::'.$attributes[$method_num]}=
	sub : lvalue {$_[0]->[$method_num]};
      ## use critic
    }
  }
  sub attributes {@attributes}

Now, if a user calls My::TX->new(p1=>..., _p3=>...) the inherited constructor initializes $self->p1 but prints a warning for _p3. _p3 begins with an underline and hence is treated as private. _p3 will not be assinged.

Optionally you can also define an init() method to initialize private data and process left over parameters:

package My::TX;
sub {
  my ($I, %param)=@_;
  $I->_p3=some_processing(delete $param{p3});
  return $I->SUPER::init(%param);
}

or slightly more effective:

package My::TX;
sub {
  my ($I, %param)=@_;
  $I->_p3=some_processing(delete $param{p3});
  @_=($I, %param);
  goto \&TX::init;
}

The init() method must delete the parameters it knows about from @_ and return the rest. So, this is also valid:

package My::TX;
sub {
  my ($I, %param)=@_;
  $I->SUPER::init;
  $I->_p3=some_processing(delete $param{p3});
  return %param;
}

Note, you must call TX::init at some point.

AUTHOR

Torsten Foertsch, <torsten.foertsch@gmx.net<gt>

COPYRIGHT AND LICENSE

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

To install TX, copy and paste the appropriate command in to your terminal.

cpanm

cpanm TX

CPAN shell

perl -MCPAN -e shell
install TX

For more information on module installation, please visit the detailed CPAN module installation guide.

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