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1 | # vim: ts=8:sw=4:sts=4:et |
2 | package DBIx::Class::Tree::AdjacencyList; |
3 | use strict; |
4 | use warnings; |
5 | use base qw( DBIx::Class ); |
6 | use Carp qw( croak ); |
7 | |
8 | =head1 NAME |
9 | |
10 | DBIx::Class::Tree::AdjacencyList - Manage a tree of data using the common adjacency list model. (EXPERIMENTAL) |
11 | |
12 | =head1 SYNOPSIS |
13 | |
14 | Create a table for your tree data. |
15 | |
16 | CREATE TABLE employees ( |
17 | employee_id INTEGER PRIMARY KEY AUTOINCREMENT, |
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18 | parent_id INTEGER NOT NULL DEFAULT 0, |
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19 | name TEXT NOT NULL |
20 | ); |
21 | |
22 | In your Schema or DB class add Tree::AdjacencyList to the top |
23 | of the component list. |
24 | |
25 | __PACKAGE__->load_components(qw( Tree::AdjacencyList ... )); |
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26 | |
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27 | Specify the column that contains the parent ID of each row. |
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28 | |
29 | package My::Employee; |
30 | __PACKAGE__->parent_column('parent_id'); |
31 | |
32 | Thats it, now you can modify and analyze the tree. |
33 | |
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34 | #!/usr/bin/perl |
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35 | use My::Employee; |
36 | |
37 | my $employee = My::Employee->create({ name=>'Matt S. Trout' }); |
38 | |
39 | my $rs = $employee->children(); |
40 | my @siblings = $employee->children(); |
41 | |
42 | my $parent = $employee->parent(); |
43 | $employee->parent( 7 ); |
44 | |
45 | =head1 DESCRIPTION |
46 | |
47 | This module provides methods for working with adjacency lists. The |
48 | adjacency list model is a very common way of representing a tree structure. |
49 | In this model each row in a table has a prent ID column that references the |
50 | primary key of another row in the same table. Because of this the primary |
51 | key must only be one column and is usually some sort of integer. The row |
52 | with a parent ID of 0 is the root row and is usually the parent of all |
53 | other rows. |
54 | |
55 | =head1 METHODS |
56 | |
57 | =head2 parent_column |
58 | |
59 | __PACKAGE__->parent_column('parent_id'); |
60 | |
61 | Declares the name of the column that contains the self-referential |
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62 | ID which defines the parent row. Defaults to "parent_id". This |
63 | will create a has_many (children) and belongs_to (parent) |
64 | relationship. |
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65 | |
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66 | =cut |
67 | |
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68 | __PACKAGE__->mk_classdata( '_parent_column' => 'parent_id' ); |
69 | |
70 | sub parent_column { |
71 | my $class = shift; |
72 | if (@_) { |
73 | my $parent_col = shift; |
74 | my $primary_col = ($class->primary_columns())[0]; |
75 | $class->belongs_to( '_parent' => $class => { "foreign.$primary_col" => "self.$parent_col" } ); |
76 | $class->has_many( 'children' => $class => { "foreign.$parent_col" => "self.$primary_col" } ); |
77 | $class->_parent_column( $parent_col ); |
78 | return 1; |
79 | } |
80 | return $class->_parent_column(); |
81 | } |
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82 | |
83 | =head2 parent |
84 | |
85 | my $parent = $employee->parent(); |
86 | $employee->parent( $parent_obj ); |
87 | $employee->parent( $parent_id ); |
88 | |
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89 | Retrieves the object's parent object, or changes the object's |
90 | parent to the specified parent or parent ID. |
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91 | |
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92 | =cut |
93 | |
94 | sub parent { |
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95 | my $self = shift; |
96 | if (@_) { |
97 | my $new_parent = shift; |
98 | my $parent_col = $self->_parent_column(); |
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99 | if (ref($new_parent)) { |
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100 | $new_parent = $new_parent->id() || croak('Parent object does not have an ID');; |
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101 | } |
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102 | return 0 if ($new_parent == ($self->get_column($parent_col)||0)); |
103 | $self->set_column( $parent_col => $new_parent ); |
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104 | $self->update(); |
105 | return 1; |
106 | } |
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107 | return $self->_parent(); |
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108 | } |
109 | |
110 | =head2 children |
111 | |
112 | my $children_rs = $employee->children(); |
113 | my @children = $employee->children(); |
114 | |
115 | Returns a list or record set, depending on context, of all |
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116 | the objects one level below the current one. This method |
117 | is created when parent_column() is called, which sets up a |
118 | has_many relationship called children. |
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119 | |
120 | =head2 attach_child |
121 | |
122 | $parent->attach_child( $child ); |
123 | |
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124 | Sets the child to the new parent. |
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125 | |
126 | =cut |
127 | |
128 | sub attach_child { |
129 | my( $self, $child ) = @_; |
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130 | return $child->parent( $self ); |
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131 | } |
132 | |
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133 | =head2 siblings |
134 | |
135 | my $rs = $node->siblings(); |
136 | my @siblings = $node->siblings(); |
137 | |
138 | Returns either a result set or an array of all other objects |
139 | with the same parent as the calling object. |
140 | |
141 | =cut |
142 | |
143 | sub siblings { |
144 | my( $self ) = @_; |
145 | my $parent_col = $self->_parent_column; |
146 | my $primary_col = ($self->primary_columns())[0]; |
147 | my $rs = $self->result_source->resultset->search( |
148 | { |
149 | $parent_col => $self->get_column($parent_col), |
150 | $primary_col => { '!=' => $self->get_column($primary_col) }, |
151 | }, |
152 | ); |
153 | return $rs->all() if (wantarray()); |
154 | return $rs; |
155 | } |
156 | |
157 | =cut |
158 | |
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159 | =head2 attach_sibling |
160 | |
161 | $this->attach_sibling( $that ); |
162 | |
163 | Sets the passed in object to have the same parent |
164 | as the calling object. |
165 | |
166 | =cut |
167 | |
168 | sub attach_sibling { |
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169 | my( $self, $node ) = @_; |
170 | return $node->parent( $self->parent() ); |
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171 | } |
172 | |
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173 | 1; |
174 | __END__ |
175 | |
176 | =head1 AUTHOR |
177 | |
178 | Aran Clary Deltac <bluefeet@cpan.org> |
179 | |
180 | =head1 LICENSE |
181 | |
182 | You may distribute this code under the same terms as Perl itself. |
183 | |