#
# Copyright (C) 1998 Ken MacLeod
# XML::Grove::Subst is free software; you can redistribute it
# and/or modify it under the same terms as Perl itself.
#
# $Id: Subst.pm,v 1.3 1999/08/25 16:49:32 kmacleod Exp $
#
use strict;
package XML::Grove::Subst;
sub new {
my $class = shift;
return bless {}, $class;
}
sub subst {
my $self = shift;
my $grove_fragment = shift;
my $args = [ @_ ];
return ($grove_fragment->accept($self, $args));
}
sub subst_hash {
my $self = shift;
my $grove_fragment = shift;
my $args = shift;
return ($grove_fragment->accept($self, $args));
}
sub visit_document {
my $self = shift; my $document = shift;
my $contents = [ $document->children_accept ($self, @_) ];
return
XML::Grove::Document->new( Contents => $contents );
}
sub visit_element {
my $self = shift; my $element = shift;
my $name = $element->{Name};
if ($name eq 'SUB:key') {
my $subst = $_[0]{$element->{Attributes}{'key'}};
if (ref($subst) eq 'ARRAY') {
return @$subst;
} else {
if (ref($subst)) {
return $subst;
} else {
return XML::Grove::Characters->new( Data => $subst );
}
}
} elsif ($name =~ /^SUB:(.*)$/) {
my $subst = $_[0][$1 - 1];
if (ref($subst) eq 'ARRAY') {
return @$subst;
} else {
if (ref($subst)) {
return $subst;
} else {
return XML::Grove::Characters->new( Data => $subst );
}
}
}
my $contents = [ $element->children_accept ($self, @_) ];
return
XML::Grove::Element->new( Name => $name,
Nttributes => $element->{Attributes},
Contents => $contents );
}
sub visit_pi {
my $self = shift; my $pi = shift;
return $pi;
}
sub visit_characters {
my $self = shift; my $characters = shift;
return $characters;
}
###
### Extend the XML::Grove::Document and XML::Grove::Element packages with our
### new function.
###
package XML::Grove::Document;
sub subst {
my $self = shift;
return (XML::Grove::Subst->new->subst($self, @_));
}
sub subst_hash {
my $self = shift;
return (XML::Grove::Subst->new->subst_hash($self, @_));
}
package XML::Grove::Element;
sub subst {
my $self = shift;
return (XML::Grove::Subst->new->subst($self, @_));
}
sub subst_hash {
my $self = shift;
return (XML::Grove::Subst->new->subst_hash($self, @_));
}
1;
__END__
=head1 NAME
XML::Grove::Subst - substitute values into a template
=head1 SYNOPSIS
use XML::Grove::Subst;
# Using subst method on XML::Grove::Document or XML::Grove::Element:
$new_grove = $source_grove->subst( ARGS );
$new_grove = $source_grove->subst_hash( ARG );
# Using an XML::Grove::Subst instance:
$subster = XML::Grove::Subst->new();
$new_grove = $subster->subst( $source_grove, ARGS );
$new_grove = $subster->subst_hash( $source_grove, ARG );
=head1 DESCRIPTION
C<XML::Grove::Subst> implements XML templates. C<XML::Grove::Subst>
traverses through a source grove replacing all elements with names
`C<SUB:XXX>' or `C<SUB:key>' with their corresponding values from ARGS (a
list) or ARG (a hash), repsectively.
=head1 METHODS
=over 4
=item $grove_obj->subst( I<ARGS> )
=item $subster->subst( $grove_obj, I<ARGS> )
Search for `C<SUB:I<XXX>>' elements, where I<XXX> is an array index,
and replace the element with the value from I<ARGS>, a list of values.
The return value is a new grove with the substitutions applied.
=item $grove_obj->subst_hash( I<ARG> )
=item $subster->subst_hash( $grove_obj, I<ARG> )
Search for `C<SUB:key>' elements and replace the element with the
value from I<ARG>, a hash of values. The hash key is taken from the
`C<key>' attribute of the `C<SUB:key>' element, for example,
`C<E<lt>SUB:key key='foo'E<gt>>'. The return value is a new grove
with the substitutions applied.
=head1 EXAMPLE
The following template, in a file `C<template.xml>', could be used for
a simple parts database conversion to HTML:
<html>
<head>
<title><SUB:key key='Name'></title>
</head>
<body>
<h1><SUB:key key='Name'></title>
<p>Information for part number <SUB:key key='Number'>:</p>
<SUB:key key='Description'>
</body>
</html>
To use this template you would first parse it and convert it to a
grove, and then use `C<subst_hash()>' every time you needed a new
page:
use XML::Parser::PerlSAX;
use XML::Grove;
use XML::Grove::Builder;
use XML::Grove::Subst;
use XML::Grove::PerlSAX;
use XML::Handler::XMLWriter;
# Load the template
$b = XML::Grove::Builder->new();
$p = XML::Parser::PerlSAX->new( Handler = $b );
$source_grove = $p->parse( Source => { SystemId => 'template.xml' } );
# Apply the substitutions
$new_grove = $source_grove->subst_hash( { Name => 'Acme DCX-2000 Filter',
Number => 'N4728',
Description => 'The Best' } );
# Write the new grove to standard output
$w = XML::Handler::XMLWriter->new();
$wp = XML::Grove::PerlSAX->new( Handler => $w );
$wp->parse( Source => { Grove => $new_grove } );
=head1 AUTHOR
Ken MacLeod, ken@bitsko.slc.ut.us
=head1 SEE ALSO
perl(1), XML::Grove(3)
Extensible Markup Language (XML) <http://www.w3c.org/XML>
=cut