+# vim: ts=8:sw=4:sts=4:et
+package DBIx::Class::Tree::AdjacencyList;
+use strict;
+use warnings;
+use base qw( DBIx::Class );
+
+=head1 NAME
+
+DBIx::Class::Tree::AdjacencyList - Manage a tree of data using the common adjacency list model.
+
+=head1 SYNOPSIS
+
+Create a table for your tree data.
+
+ CREATE TABLE employees (
+ employee_id INTEGER PRIMARY KEY AUTOINCREMENT,
+ parent_id INTEGER NOT NULL,
+ name TEXT NOT NULL
+ );
+
+In your Schema or DB class add Tree::AdjacencyList to the top
+of the component list.
+
+ __PACKAGE__->load_components(qw( Tree::AdjacencyList ... ));
+ # If you want positionable data make sure this
+ # module comes first, as in:
+ __PACKAGE__->load_components(qw( Tree::AdjacencyList Positioned ... ));
+
+Specify the column that contains the parent ID each row.
+
+ package My::Employee;
+ __PACKAGE__->parent_column('parent_id');
+
+Thats it, now you can modify and analyze the tree.
+
+ #!/use/bin/perl
+ use My::Employee;
+
+ my $employee = My::Employee->create({ name=>'Matt S. Trout' });
+
+ my $rs = $employee->children();
+ my @siblings = $employee->children();
+
+ my $parent = $employee->parent();
+ $employee->parent( 7 );
+
+=head1 DESCRIPTION
+
+This module provides methods for working with adjacency lists. The
+adjacency list model is a very common way of representing a tree structure.
+In this model each row in a table has a prent ID column that references the
+primary key of another row in the same table. Because of this the primary
+key must only be one column and is usually some sort of integer. The row
+with a parent ID of 0 is the root row and is usually the parent of all
+other rows.
+
+=head1 METHODS
+
+=head2 parent_column
+
+ __PACKAGE__->parent_column('parent_id');
+
+Declares the name of the column that contains the self-referential
+ID which defines the parent row. Defaults to "parent_id".
+
+=cut
+
+__PACKAGE__->mk_classdata( 'parent_column' => 'parent_id' );
+
+=head2 parent
+
+ my $parent = $employee->parent();
+ $employee->parent( $parent_obj );
+ $employee->parent( $parent_id );
+
+Retrieves the object's parent ID, or sets the object's
+parent ID. If setting the parent ID then 0 will be returned
+if the object already has the specified parent, and 1 on
+success.
+
+If you are using the Positioned component this
+module will first move the object to the last position of
+the list, change the parent ID, then move the object to the
+last position of the new list. This ensures the intergrity
+of the positions.
+
+=cut
+
+sub parent {
+ my( $self, $new_parent ) = @_;
+ my $parent_column = $self->parent_column();
+ if ($new_parent) {
+ if (ref($new_parent)) {
+ $new_parent = $new_parent->id();
+ }
+ return 0 if ($new_parent == $self->get_column($parent_column));
+ my $positioned = $self->can('position_column');
+ $self->move_last if ($positioned);
+ $self->set_column( $parent_column => $new_parent );
+ if ($positioned) {
+ $self->set_column(
+ $self->position_column() => $self->search( {$self->_parent_clause()} )->count() + 1
+ );
+ }
+ $self->update();
+ return 1;
+ }
+ else {
+ return $self->find( $self->get_column( $parent_column ) );
+ }
+}
+
+=head2 children
+
+ my $children_rs = $employee->children();
+ my @children = $employee->children();
+
+Returns a list or record set, depending on context, of all
+the objects one level below the current one.
+
+If you are using the Positioned component then this method
+will return the children sorted by the position column.
+
+=cut
+
+sub children {
+ my( $self ) = @_;
+ my $rs = $self->search(
+ { $self->parent_column()=>$self->id() },
+ ( $self->can('position_column') ? {order_by=>$self->position_column()} : () )
+ );
+ return $rs->all() if (wantarray());
+ return $rs;
+}
+
+=head2 descendents
+
+Same as children. Declared so that this module is
+compatible with the Tree::NestedSet module.
+
+=cut
+
+#*descendants = \&children;
+
+=head1 PRIVATE METHODS
+
+These methods are used internally. You should never have the
+need to use them.
+
+=head2 _parent_clause
+
+This method is provided as an override of the method in
+DBIC::Positioned. This way Positioned and Tree::AdjacencyList
+may be used together without conflict. Make sure that in
+you component list that you load Tree::AdjacencyList before you
+load Positioned.
+
+This method assumes a parent ID of 0 if none is defined. This
+usually comes in to play if you are just createing the object
+and it has not yet been assigned a parent.
+
+=cut
+
+sub _parent_clause {
+ my( $self ) = @_;
+ return (
+ $self->parent_column() =>
+ $self->get_column($self->parent_column()) || 0
+ );
+}
+
+1;
+__END__
+
+=head1 AUTHOR
+
+Aran Deltac <bluefeet@cpan.org>
+
+=head1 LICENSE
+
+You may distribute this code under the same terms as Perl itself.
+
projects / dbsrgits/DBIx-Class.git / blobdiff