NAME

DBIx::Class::Tree::CalculateSets

SYNOPSIS

  # Imagine if you will, a database table looking somewhat like this:
  # CREATE TABLE foo (
  #   id     serial PRIMARY KEY,
  #   parent integer,
  #   root   integer,
  #   lft    integer,
  #   rgt    integer,
  #   name   text,
  # );

  # And imagine we have a DBIx::Class::Result::Foo module containing
  # among other things the following line:
  #
  # __PACKAGE__->load_components(qw/Tree::CalculateSets Core/);

  my $rs = $schema->resultset ('Foo');

  # An initial root node

  my $root = $rs->create ({ name => 'root' });

  # Make sure column 'root' is assigned. DBIx::Class can do this
  # automagically for further children of the root node.

  $root->update ({ root => $root->id });

  # Create a few children from root

  $root->children->create ({ name => 'level 2 a' });

  my $child = $root->children->create ({ name => 'level 2 b' });

  # Give one of the root children its own child node

  my $child2 = $child->children->create ({ name => 'level 3' });

  # This will populate the lft and rgt columns in the entire tree

  $root->calculate_sets;

  # Print $child and all its children. discard_changes is called so
  # that our object is forced to retrieve the changes made by
  # calculate_sets from the database.

  $child->discard_changes;

  print $_->name . "\n" for $rs->search ({
      lft => { '>=' => $child->lft },
      rgt => { '<=' => $child->rgt },
    });

  # Print all children of $root (Same results)

  $root->discard_changes;

  print $_->name . "\n" for $rs->search ({
      lft => { '>' => $root->lft },
      rgt => { '<' => $root->rgt },
    });

  # Print $child2 and all parents

  $child2->discard_changes;

  print $_->name . "\n" for $rs->search ({
      lft => { '<=' => $child2->lft },
      rgt => { '>=' => $child2->rgt },
    });

DESCRIPTION

This is a small utility module that lets you calculate nested sets from an ordinary parent column based tree structure, allowing you to trivially search an entire tree path. Note however, that constructing the search itself is outside the scope of this module, but the synopsis should hopefully give you a good idea of how to do it yourself.

METHODS

left_column

  __PACKAGE__->left_column('lft'); # The default value

right_column

  __PACKAGE__->right_column('rgt'); # Also the default

root_column

  __PACKAGE__->root_column('root'); # Yes, 'root' is default

The name of the column storing the id of the root column. Another way to think of this column is as the id of the tree the current node belongs to.

child_relationship

  __PACKAGE__->child_relationship('children'); # Yeah..

The name of the relationship used to find child nodes of the current node.

is_root

  if ($node->is_root) { }

Returns true if the current node is the root node.

calculate_sets

  $root->calculate_sets;

Populates the left_column and right_column columns of the entire tree with the correct nested set values.

AUTHOR

Anders Nor Berle <berle@cpan.org>

COPYRIGHT AND LICENSE

Copyright (c) 2009 Anders Nor Berle

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.