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#============================================================= -*-Perl-*-
#
# Template::Plugin::Filter
#
# DESCRIPTION
# Template Toolkit module implementing a base class plugin
# object which acts like a filter and can be used with the
# FILTER directive.
#
# AUTHOR
# Andy Wardley <abw@wardley.org>
#
# COPYRIGHT
# Copyright (C) 2001-2022 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.
#
#============================================================================
package Template::Plugin::Filter;
use strict;
use warnings;
use base 'Template::Plugin';
use Scalar::Util 'weaken', 'isweak';
our $VERSION = '3.100';
our $DYNAMIC = 0 unless defined $DYNAMIC;
sub new {
my ($class, $context, @args) = @_;
my $config = @args && ref $args[-1] eq 'HASH' ? pop(@args) : { };
# look for $DYNAMIC
my $dynamic;
{
no strict 'refs';
$dynamic = ${"$class\::DYNAMIC"};
}
$dynamic = $DYNAMIC unless defined $dynamic;
my $self = bless {
_CONTEXT => $context,
_DYNAMIC => $dynamic,
_ARGS => \@args,
_CONFIG => $config,
}, $class;
return $self->init($config)
|| $class->error($self->error());
}
sub init {
my ($self, $config) = @_;
return $self;
}
sub factory {
my $self = shift;
my $this = $self;
# avoid a memory leak
weaken( $this->{_CONTEXT} ) if ref $this->{_CONTEXT}
&& !isweak $this->{_CONTEXT};
if ($self->{ _DYNAMIC }) {
return [ sub {
my ($context, @args) = @_;
my $config = ref $args[-1] eq 'HASH' ? pop(@args) : { };
return sub {
$this->filter(shift, \@args, $config);
};
}, 1 ];
}
else {
return sub {
$this->filter(shift);
};
}
}
sub filter {
my ($self, $text, $args, $config) = @_;
return $text;
}
sub merge_config {
my ($self, $newcfg) = @_;
my $owncfg = $self->{ _CONFIG };
return $owncfg unless $newcfg;
return { %$owncfg, %$newcfg };
}
sub merge_args {
my ($self, $newargs) = @_;
my $ownargs = $self->{ _ARGS };
return $ownargs unless $newargs;
return [ @$ownargs, @$newargs ];
}
sub install_filter {
my ($self, $name) = @_;
$self->{ _CONTEXT }->define_filter( $name => $self->factory );
return $self;
}
1;
__END__
=head1 NAME
Template::Plugin::Filter - Base class for plugin filters
=head1 SYNOPSIS
package MyOrg::Template::Plugin::MyFilter;
use Template::Plugin::Filter;
use base qw( Template::Plugin::Filter );
sub filter {
my ($self, $text) = @_;
# ...mungify $text...
return $text;
}
# now load it...
[% USE MyFilter %]
# ...and use the returned object as a filter
[% FILTER $MyFilter %]
...
[% END %]
=head1 DESCRIPTION
This module implements a base class for plugin filters. It hides
the underlying complexity involved in creating and using filters
that get defined and made available by loading a plugin.
To use the module, simply create your own plugin module that is
inherited from the C<Template::Plugin::Filter> class.
package MyOrg::Template::Plugin::MyFilter;
use Template::Plugin::Filter;
use base qw( Template::Plugin::Filter );
Then simply define your C<filter()> method. When called, you get
passed a reference to your plugin object (C<$self>) and the text
to be filtered.
sub filter {
my ($self, $text) = @_;
# ...mungify $text...
return $text;
}
To use your custom plugin, you have to make sure that the Template
Toolkit knows about your plugin namespace.
my $tt2 = Template->new({
PLUGIN_BASE => 'MyOrg::Template::Plugin',
});
Or for individual plugins you can do it like this:
my $tt2 = Template->new({
PLUGINS => {
MyFilter => 'MyOrg::Template::Plugin::MyFilter',
},
});
Then you C<USE> your plugin in the normal way.
[% USE MyFilter %]
The object returned is stored in the variable of the same name,
'C<MyFilter>'. When you come to use it as a C<FILTER>, you should add
a dollar prefix. This indicates that you want to use the filter
stored in the variable 'C<MyFilter>' rather than the filter named
'C<MyFilter>', which is an entirely different thing (see later for
information on defining filters by name).
[% FILTER $MyFilter %]
...text to be filtered...
[% END %]
You can, of course, assign it to a different variable.
[% USE blat = MyFilter %]
[% FILTER $blat %]
...text to be filtered...
[% END %]
Any configuration parameters passed to the plugin constructor from the
C<USE> directive are stored internally in the object for inspection by
the C<filter()> method (or indeed any other method). Positional
arguments are stored as a reference to a list in the C<_ARGS> item while
named configuration parameters are stored as a reference to a hash
array in the C<_CONFIG> item.
For example, loading a plugin as shown here:
[% USE blat = MyFilter 'foo' 'bar' baz = 'blam' %]
would allow the C<filter()> method to do something like this:
sub filter {
my ($self, $text) = @_;
my $args = $self->{ _ARGS }; # [ 'foo', 'bar' ]
my $conf = $self->{ _CONFIG }; # { baz => 'blam' }
# ...munge $text...
return $text;
}
By default, plugins derived from this module will create static
filters. A static filter is created once when the plugin gets
loaded via the C<USE> directive and re-used for all subsequent
C<FILTER> operations. That means that any argument specified with
the C<FILTER> directive are ignored.
Dynamic filters, on the other hand, are re-created each time
they are used by a C<FILTER> directive. This allows them to act
on any parameters passed from the C<FILTER> directive and modify
their behaviour accordingly.
There are two ways to create a dynamic filter. The first is to
define a C<$DYNAMIC> class variable set to a true value.
package MyOrg::Template::Plugin::MyFilter;
use base 'Template::Plugin::Filter';
our $DYNAMIC = 1;
The other way is to set the internal C<_DYNAMIC> value within the C<init()>
method which gets called by the C<new()> constructor.
sub init {
my $self = shift;
$self->{ _DYNAMIC } = 1;
return $self;
}
When this is set to a true value, the plugin will automatically
create a dynamic filter. The outcome is that the C<filter()> method
will now also get passed a reference to an array of positional
arguments and a reference to a hash array of named parameters.
So, using a plugin filter like this:
[% FILTER $blat 'foo' 'bar' baz = 'blam' %]
would allow the C<filter()> method to work like this:
sub filter {
my ($self, $text, $args, $conf) = @_;
# $args = [ 'foo', 'bar' ]
# $conf = { baz => 'blam' }
}
In this case can pass parameters to both the USE and FILTER directives,
so your filter() method should probably take that into account.
[% USE MyFilter 'foo' wiz => 'waz' %]
[% FILTER $MyFilter 'bar' biz => 'baz' %]
...
[% END %]
You can use the C<merge_args()> and C<merge_config()> methods to do a quick
and easy job of merging the local (e.g. C<FILTER>) parameters with the
internal (e.g. C<USE>) values and returning new sets of conglomerated
data.
sub filter {
my ($self, $text, $args, $conf) = @_;
$args = $self->merge_args($args);
$conf = $self->merge_config($conf);
# $args = [ 'foo', 'bar' ]
# $conf = { wiz => 'waz', biz => 'baz' }
...
}
You can also have your plugin install itself as a named filter by
calling the C<install_filter()> method from the C<init()> method. You
should provide a name for the filter, something that you might
like to make a configuration option.
sub init {
my $self = shift;
my $name = $self->{ _CONFIG }->{ name } || 'myfilter';
$self->install_filter($name);
return $self;
}
This allows the plugin filter to be used as follows:
[% USE MyFilter %]
[% FILTER myfilter %]
...
[% END %]
or
[% USE MyFilter name = 'swipe' %]
[% FILTER swipe %]
...
[% END %]
Alternately, you can allow a filter name to be specified as the
first positional argument.
sub init {
my $self = shift;
my $name = $self->{ _ARGS }->[0] || 'myfilter';
$self->install_filter($name);
return $self;
}
[% USE MyFilter 'swipe' %]
[% FILTER swipe %]
...
[% END %]
=head1 EXAMPLE
Here's a complete example of a plugin filter module.
package My::Template::Plugin::Change;
use Template::Plugin::Filter;
use base qw( Template::Plugin::Filter );
sub init {
my $self = shift;
$self->{ _DYNAMIC } = 1;
# first arg can specify filter name
$self->install_filter($self->{ _ARGS }->[0] || 'change');
return $self;
}
sub filter {
my ($self, $text, $args, $config) = @_;
$config = $self->merge_config($config);
my $regex = join('|', keys %$config);
$text =~ s/($regex)/$config->{ $1 }/ge;
return $text;
}
1;
=head1 AUTHOR
Andy Wardley E<lt>abw@wardley.orgE<gt> L<http://wardley.org/>
=head1 COPYRIGHT
Copyright (C) 1996-2022 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.
=head1 SEE ALSO
L<Template::Plugin>, L<Template::Filters>, L<Template::Manual::Filters>
=cut
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