—
—
—

              
package CQL::Visitor;
use strict;
use warnings;
HideShow 46 lines of Pod
=head1 NAME
CQL::Visitor - visit nodes in a CQL parse tree
=head1 SYNOPSIS
    package MyVisitor;
    use base qw( CQL::Visitor );
    sub term {
        my ($self,$node) = @_;
        # do something to the node
    }
    # later on
    
    my $parser = CQL::Parser->new();
    my $root = $parser->parse($cql);
    my $visitor = MyVisitor->new();
    $vistor->visit($root);
=head1 DESCRIPTION
CQL::Visitor provides a simple interface for visiting nodes in your parse tree.
It could be useful if you want to do something like change a query like this:
    dc.title=foo and dc.creator=bar 
    into
    title=foo and creator=bar
Or some similar procedure. You simply create a new subclass of CQL::Visitor
and override the appropriate method, such as term(). Every term that is
encountered during the traversal will be handed off to your term() method.
Note: at the moment only term() is supported because that's what was needed, but
if you need other ones feel free to add them, or ask for them.
=head1 METHODS
=head2 new()
=cut
sub new {
    my $class = shift;
    return bless {}, ref($class) || $class;
}
HideShow 6 lines of Pod
=head2 visit()
Call this to traverse your parse tree, starting at the root.
=cut
sub visit {
    my ($self,$node) = @_;
    if ( $node->isa( 'CQL::BooleanNode' ) ) { 
        $self->visit( $node->left() );
        $self->visit( $node->right() );
    }
    elsif ( $node->isa( 'CQL::TermNode' ) ) {
        $self->term( $node );
    }
}
HideShow 7 lines of Pod
=head2 term()
Your subclass should override this, and do something meaningful with the
CQL::TermNode object.
=cut
sub term {
    # subclasses should subclass
}
1;