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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 |
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52 | with a parent ID of 0 is the root node and is usually the parent of all |
53 | other rows. Although, there is no limitation in this module that would |
54 | stop you from having multiple root nodes. |
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55 | |
56 | =head1 METHODS |
57 | |
58 | =head2 parent_column |
59 | |
60 | __PACKAGE__->parent_column('parent_id'); |
61 | |
62 | Declares the name of the column that contains the self-referential |
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63 | ID which defines the parent row. Defaults to "parent_id". This |
64 | will create a has_many (children) and belongs_to (parent) |
65 | relationship. |
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66 | |
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67 | =cut |
68 | |
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69 | __PACKAGE__->mk_classdata( '_parent_column' => 'parent_id' ); |
70 | |
71 | sub parent_column { |
72 | my $class = shift; |
73 | if (@_) { |
74 | my $parent_col = shift; |
75 | my $primary_col = ($class->primary_columns())[0]; |
76 | $class->belongs_to( '_parent' => $class => { "foreign.$primary_col" => "self.$parent_col" } ); |
77 | $class->has_many( 'children' => $class => { "foreign.$parent_col" => "self.$primary_col" } ); |
78 | $class->_parent_column( $parent_col ); |
79 | return 1; |
80 | } |
81 | return $class->_parent_column(); |
82 | } |
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83 | |
84 | =head2 parent |
85 | |
86 | my $parent = $employee->parent(); |
87 | $employee->parent( $parent_obj ); |
88 | $employee->parent( $parent_id ); |
89 | |
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90 | Retrieves the object's parent object, or changes the object's |
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91 | parent to the specified parent or parent ID. If you would like |
92 | to make the object the root node, just set the parent to 0. |
93 | |
94 | If you are setting the parent then 0 will be returned if the |
95 | specified parent is already the object's parent and 1 on |
96 | success. |
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97 | |
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98 | =cut |
99 | |
100 | sub parent { |
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101 | my $self = shift; |
102 | if (@_) { |
103 | my $new_parent = shift; |
104 | my $parent_col = $self->_parent_column(); |
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105 | if (ref($new_parent)) { |
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106 | $new_parent = $new_parent->id() || croak('Parent object does not have an ID');; |
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107 | } |
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108 | return 0 if ($new_parent == ($self->get_column($parent_col)||0)); |
109 | $self->set_column( $parent_col => $new_parent ); |
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110 | $self->update(); |
111 | return 1; |
112 | } |
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113 | return $self->_parent(); |
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114 | } |
115 | |
116 | =head2 children |
117 | |
118 | my $children_rs = $employee->children(); |
119 | my @children = $employee->children(); |
120 | |
121 | Returns a list or record set, depending on context, of all |
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122 | the objects one level below the current one. This method |
123 | is created when parent_column() is called, which sets up a |
124 | has_many relationship called children. |
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125 | |
126 | =head2 attach_child |
127 | |
128 | $parent->attach_child( $child ); |
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129 | $parent->attach_child( $child, $child, ... ); |
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130 | |
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131 | Sets the child, or children, to the new parent. Returns 1 |
132 | on success and returns 0 if the parent object already has |
133 | the child. |
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134 | |
135 | =cut |
136 | |
137 | sub attach_child { |
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138 | my $self = shift; |
139 | my $return = 1; |
140 | foreach my $child (@_) { |
141 | $child->parent( $self ); |
142 | } |
143 | return $return; |
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144 | } |
145 | |
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146 | =head2 siblings |
147 | |
148 | my $rs = $node->siblings(); |
149 | my @siblings = $node->siblings(); |
150 | |
151 | Returns either a result set or an array of all other objects |
152 | with the same parent as the calling object. |
153 | |
154 | =cut |
155 | |
156 | sub siblings { |
157 | my( $self ) = @_; |
158 | my $parent_col = $self->_parent_column; |
159 | my $primary_col = ($self->primary_columns())[0]; |
160 | my $rs = $self->result_source->resultset->search( |
161 | { |
162 | $parent_col => $self->get_column($parent_col), |
163 | $primary_col => { '!=' => $self->get_column($primary_col) }, |
164 | }, |
165 | ); |
166 | return $rs->all() if (wantarray()); |
167 | return $rs; |
168 | } |
169 | |
170 | =cut |
171 | |
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172 | =head2 attach_sibling |
173 | |
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174 | $obj->attach_sibling( $sibling ); |
175 | $obj->attach_sibling( $sibling, $sibling, ... ); |
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176 | |
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177 | Sets the passed in object(s) to have the same parent |
178 | as the calling object. Returns 1 on success and |
179 | 0 if the sibling already has the same parent. |
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180 | |
181 | =cut |
182 | |
183 | sub attach_sibling { |
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184 | my $self = shift; |
185 | my $return = 1; |
186 | foreach my $node (@_) { |
187 | $return = 0 if (!$node->parent( $self->parent() )); |
188 | } |
189 | return $return; |
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190 | } |
191 | |
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192 | 1; |
193 | __END__ |
194 | |
195 | =head1 AUTHOR |
196 | |
197 | Aran Clary Deltac <bluefeet@cpan.org> |
198 | |
199 | =head1 LICENSE |
200 | |
201 | You may distribute this code under the same terms as Perl itself. |
202 | |