-# vim: ts=8:sw=4:sts=4:et
package DBIx::Class::Tree::AdjacencyList;
+# vim: ts=8:sw=4:sts=4:et
+
use strict;
use warnings;
+
use base qw( DBIx::Class );
use Carp qw( croak );
=head1 NAME
-DBIx::Class::Tree::AdjacencyList - Manage a tree of data using the common adjacency list model. (EXPERIMENTAL)
+DBIx::Class::Tree::AdjacencyList - Manage a tree of data using the common adjacency list model.
=head1 SYNOPSIS
name TEXT NOT NULL
);
-In your Schema or DB class add Tree::AdjacencyList to the top
+In your Schema or DB class add Tree::AdjacencyList to the top
of the component list.
__PACKAGE__->load_components(qw( Tree::AdjacencyList ... ));
package My::Employee;
__PACKAGE__->parent_column('parent_id');
+Optionally, automatically maintane a consistent tree structure.
+
+ __PACKAGE__->repair_tree( 1 );
+
Thats it, now you can modify and analyze the tree.
#!/usr/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 node and is usually the parent of all
-other rows. Although, there is no limitation in this module that would
+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 node and is usually the parent of all
+other rows. Although, there is no limitation in this module that would
stop you from having multiple root nodes.
=head1 METHODS
__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". This
-will create a has_many (children) and belongs_to (parent)
-relationship.
+Declares the name of the column that contains the self-referential
+ID which defines the parent row. This will create a has_many (children)
+and belongs_to (parent) relationship.
+
+This method also sets up an additional has_many relationship called
+parents which is useful when you want to treat an adjacency list
+as a DAG.
=cut
my $primary_col = ($class->primary_columns())[0];
$class->belongs_to( '_parent' => $class => { "foreign.$primary_col" => "self.$parent_col" } );
$class->has_many( 'children' => $class => { "foreign.$parent_col" => "self.$primary_col" } );
+ $class->has_many( 'parents' => $class => { "foreign.$primary_col" => "self.$parent_col" }, { cascade_delete => 0, cascade_copy => 0 } );
$class->_parent_column( $parent_col );
return 1;
}
return $class->_parent_column();
}
+=head2 repair_tree
+
+ __PACKAGE__->repair_tree( 1 );
+
+When set a true value this flag causes all changes to a node's parent to
+trigger an integrity check on the tree. If, when changing a node's parent
+to one of it's descendents then all its children will first be moved to have
+the same current parent, and then the node's parent is changed.
+
+So, for example, if the tree is like this:
+
+ A
+ B
+ C
+ D
+ E
+ F
+
+And you execute:
+
+ $b->parent( $d );
+
+Since D is a descendant of B then all of D's siblings get their parent
+changed to A. Then B's parent is set to D.
+
+ A
+ C
+ D
+ B
+ E
+ F
+
+=cut
+
+__PACKAGE__->mk_classdata( 'repair_tree' => 0 );
+
=head2 parent
my $parent = $employee->parent();
$employee->parent( $parent_obj );
$employee->parent( $parent_id );
-Retrieves the object's parent object, or changes the object's
-parent to the specified parent or parent ID. If you would like
+Retrieves the object's parent object, or changes the object's
+parent to the specified parent or parent ID. If you would like
to make the object the root node, just set the parent to 0.
-If you are setting the parent then 0 will be returned if the
-specified parent is already the object's parent and 1 on
+If you are setting the parent then 0 will be returned if the
+specified parent is already the object's parent and 1 on
success.
=cut
$new_parent = $new_parent->id() || croak('Parent object does not have an ID');;
}
return 0 if ($new_parent == ($self->get_column($parent_col)||0));
+
+ if ($self->repair_tree()) {
+ my $found = $self->has_descendant( $new_parent );
+ if ($found) {
+ my $children = $self->children();
+
+ while (my $child = $children->next()) {
+ $child->parent( $self->$parent_col() );
+ }
+ }
+ }
+
$self->set_column( $parent_col => $new_parent );
$self->update();
return 1;
}
return $self->_parent();
}
+=head2 ancestors
+
+ @list = $employee->ancestors();
+
+Returns a list of ancestors starting with a record's
+parent and moving toward the tree root.
+
+=cut
+
+sub ancestors {
+ my $self = shift;
+ my @ancestors = ();
+ my $rec = $self;
+ while ($rec = $rec->parent) {
+ push(@ancestors, $rec);
+ }
+ return @ancestors;
+}
+
+
+=head2 has_descendant
+
+ if ($employee->has_descendant( $id )) { ... }
+
+Returns true if the object has a descendant with the
+specified ID.
+
+=cut
+
+sub has_descendant {
+ my ($self, $find_id) = @_;
+
+ my $children = $self->children();
+ while (my $child = $children->next()) {
+ if ($child->id() eq $find_id) {
+ return 1;
+ }
+ return 1 if ($child->has_descendant( $find_id ));
+ }
+
+ return 0;
+}
+
+=head2 parents
+
+ my $parents = $node->parents();
+ my @parents = $node->parents();
+
+This has_many relationship is not that useful as it will
+never return more than one parent due to the one-to-many
+structure of adjacency lists. The reason this relationship
+is defined is so that this tree type may be treated as if
+it was a DAG.
=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. This method
-is created when parent_column() is called, which sets up a
+Returns a list or record set, depending on context, of all
+the objects one level below the current one. This method
+is created when parent_column() is called, which sets up a
has_many relationship called children.
=head2 attach_child
$parent->attach_child( $child );
$parent->attach_child( $child, $child, ... );
-Sets the child, or children, to the new parent. Returns 1
-on success and returns 0 if the parent object already has
+Sets the child, or children, to the new parent. Returns 1
+on success and returns 0 if the parent object already has
the child.
=cut
my $rs = $node->siblings();
my @siblings = $node->siblings();
-Returns either a result set or an array of all other objects
+Returns either a result set or an array of all other objects
with the same parent as the calling object.
=cut
return $rs;
}
-=cut
-
=head2 attach_sibling
$obj->attach_sibling( $sibling );
$obj->attach_sibling( $sibling, $sibling, ... );
-Sets the passed in object(s) to have the same parent
-as the calling object. Returns 1 on success and
+Sets the passed in object(s) to have the same parent
+as the calling object. Returns 1 on success and
0 if the sibling already has the same parent.
=cut
return $return;
}
+=head2 is_leaf
+
+ if ($obj->is_leaf()) { ... }
+
+Returns 1 if the object has no children, and 0 otherwise.
+
+=cut
+
+sub is_leaf {
+ my( $self ) = @_;
+
+ my $has_child = $self->result_source->resultset->search(
+ { $self->_parent_column => $self->id() },
+ { limit => 1 }
+ )->count();
+
+ return $has_child ? 0 : 1;
+}
+
+=head2 is_root
+
+ if ($obj->is_root()) { ... }
+
+Returns 1 if the object has no parent, and 0 otherwise.
+
+=cut
+
+sub is_root {
+ my( $self ) = @_;
+ return ( $self->get_column( $self->_parent_column ) ? 0 : 1 );
+}
+
+=head2 is_branch
+
+ if ($obj->is_branch()) { ... }
+
+Returns 1 if the object has a parent and has children.
+Returns 0 otherwise.
+
+=cut
+
+sub is_branch {
+ my( $self ) = @_;
+ return ( ($self->is_leaf() or $self->is_root()) ? 0 : 1 );
+}
+
+=head2 set_primary_key
+
+This method is an override of DBIx::Class' method for setting the
+class' primary key column(s). This method passes control right on
+to the normal method after first validating that only one column is
+being selected as a primary key. If more than one column is then
+an error will be thrown.
+
+=cut
+
+sub set_primary_key {
+ my $self = shift;
+ if (@_>1) {
+ croak('You may only specify a single column as the primary key for adjacency tree classes');
+ }
+ return $self->next::method( @_ );
+}
+
1;
__END__
+=head1 INHERITED METHODS
+
+=head2 DBIx::Class
+
+=over 4
+
+=item *
+
+L<mk_classdata|DBIx::Class/mk_classdata>
+
+=item *
+
+L<component_base_class|DBIx::Class/component_base_class>
+
+=back
+
+=head2 DBIx::Class::Componentised
+
+=over 4
+
+=item *
+
+L<inject_base|DBIx::Class::Componentised/inject_base>
+
+=item *
+
+L<load_components|DBIx::Class::Componentised/load_components>
+
+=item *
+
+L<load_own_components|DBIx::Class::Componentised/load_own_components>
+
+=back
+
+=head2 Class::Data::Accessor
+
+=over 4
+
+=item *
+
+L<mk_classaccessor|Class::Data::Accessor/mk_classaccessor>
+
+=back
+
=head1 AUTHOR
Aran Clary Deltac <bluefeet@cpan.org>
projects / dbsrgits/DBIx-Class-Tree.git / blobdiff