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1 | package DBIx::Class::Tree::AdjacencyList; |
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2 | # vim: ts=8:sw=4:sts=4:et |
3 | |
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4 | use strict; |
5 | use warnings; |
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6 | |
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7 | use base qw( DBIx::Class ); |
8 | use Carp qw( croak ); |
9 | |
10 | =head1 NAME |
11 | |
12 | DBIx::Class::Tree::AdjacencyList - Manage a tree of data using the common adjacency list model. (EXPERIMENTAL) |
13 | |
14 | =head1 SYNOPSIS |
15 | |
16 | Create a table for your tree data. |
17 | |
18 | CREATE TABLE employees ( |
19 | employee_id INTEGER PRIMARY KEY AUTOINCREMENT, |
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20 | parent_id INTEGER NOT NULL DEFAULT 0, |
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21 | name TEXT NOT NULL |
22 | ); |
23 | |
24 | In your Schema or DB class add Tree::AdjacencyList to the top |
25 | of the component list. |
26 | |
27 | __PACKAGE__->load_components(qw( Tree::AdjacencyList ... )); |
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28 | |
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29 | Specify the column that contains the parent ID of each row. |
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30 | |
31 | package My::Employee; |
32 | __PACKAGE__->parent_column('parent_id'); |
33 | |
34 | Thats it, now you can modify and analyze the tree. |
35 | |
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36 | #!/usr/bin/perl |
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37 | use My::Employee; |
38 | |
39 | my $employee = My::Employee->create({ name=>'Matt S. Trout' }); |
40 | |
41 | my $rs = $employee->children(); |
42 | my @siblings = $employee->children(); |
43 | |
44 | my $parent = $employee->parent(); |
45 | $employee->parent( 7 ); |
46 | |
47 | =head1 DESCRIPTION |
48 | |
49 | This module provides methods for working with adjacency lists. The |
50 | adjacency list model is a very common way of representing a tree structure. |
51 | In this model each row in a table has a prent ID column that references the |
52 | primary key of another row in the same table. Because of this the primary |
53 | key must only be one column and is usually some sort of integer. The row |
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54 | with a parent ID of 0 is the root node and is usually the parent of all |
55 | other rows. Although, there is no limitation in this module that would |
56 | stop you from having multiple root nodes. |
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57 | |
58 | =head1 METHODS |
59 | |
60 | =head2 parent_column |
61 | |
62 | __PACKAGE__->parent_column('parent_id'); |
63 | |
64 | Declares the name of the column that contains the self-referential |
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65 | ID which defines the parent row. Defaults to "parent_id". This |
66 | will create a has_many (children) and belongs_to (parent) |
67 | relationship. |
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68 | |
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69 | This method also setups an additional has_many relationship called |
70 | parents which is useful when you want to treat an adjacency list |
71 | as a DAG. |
72 | |
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73 | =cut |
74 | |
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75 | __PACKAGE__->mk_classdata( '_parent_column' => 'parent_id' ); |
76 | |
77 | sub parent_column { |
78 | my $class = shift; |
79 | if (@_) { |
80 | my $parent_col = shift; |
81 | my $primary_col = ($class->primary_columns())[0]; |
82 | $class->belongs_to( '_parent' => $class => { "foreign.$primary_col" => "self.$parent_col" } ); |
83 | $class->has_many( 'children' => $class => { "foreign.$parent_col" => "self.$primary_col" } ); |
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84 | $class->has_many( 'parents' => $class => { "foreign.$primary_col" => "self.$parent_col" } ); |
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85 | $class->_parent_column( $parent_col ); |
86 | return 1; |
87 | } |
88 | return $class->_parent_column(); |
89 | } |
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90 | |
91 | =head2 parent |
92 | |
93 | my $parent = $employee->parent(); |
94 | $employee->parent( $parent_obj ); |
95 | $employee->parent( $parent_id ); |
96 | |
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97 | Retrieves the object's parent object, or changes the object's |
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98 | parent to the specified parent or parent ID. If you would like |
99 | to make the object the root node, just set the parent to 0. |
100 | |
101 | If you are setting the parent then 0 will be returned if the |
102 | specified parent is already the object's parent and 1 on |
103 | success. |
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104 | |
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105 | =cut |
106 | |
107 | sub parent { |
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108 | my $self = shift; |
109 | if (@_) { |
110 | my $new_parent = shift; |
111 | my $parent_col = $self->_parent_column(); |
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112 | if (ref($new_parent)) { |
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113 | $new_parent = $new_parent->id() || croak('Parent object does not have an ID');; |
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114 | } |
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115 | return 0 if ($new_parent == ($self->get_column($parent_col)||0)); |
116 | $self->set_column( $parent_col => $new_parent ); |
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117 | $self->update(); |
118 | return 1; |
119 | } |
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120 | return $self->_parent(); |
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121 | } |
122 | |
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123 | =head2 parents |
124 | |
125 | my $parents = $node->parents(); |
126 | my @parents = $node->parents(); |
127 | |
128 | This has_many relationship is not that useful as it will |
129 | never return more than one parent due to the one-to-many |
130 | structure of adjacency lists. The reason this relationship |
131 | is defined is so that this tree type may be treated as if |
132 | it was a DAG. |
133 | |
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134 | =head2 children |
135 | |
136 | my $children_rs = $employee->children(); |
137 | my @children = $employee->children(); |
138 | |
139 | Returns a list or record set, depending on context, of all |
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140 | the objects one level below the current one. This method |
141 | is created when parent_column() is called, which sets up a |
142 | has_many relationship called children. |
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143 | |
144 | =head2 attach_child |
145 | |
146 | $parent->attach_child( $child ); |
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147 | $parent->attach_child( $child, $child, ... ); |
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148 | |
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149 | Sets the child, or children, to the new parent. Returns 1 |
150 | on success and returns 0 if the parent object already has |
151 | the child. |
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152 | |
153 | =cut |
154 | |
155 | sub attach_child { |
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156 | my $self = shift; |
157 | my $return = 1; |
158 | foreach my $child (@_) { |
159 | $child->parent( $self ); |
160 | } |
161 | return $return; |
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162 | } |
163 | |
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164 | =head2 siblings |
165 | |
166 | my $rs = $node->siblings(); |
167 | my @siblings = $node->siblings(); |
168 | |
169 | Returns either a result set or an array of all other objects |
170 | with the same parent as the calling object. |
171 | |
172 | =cut |
173 | |
174 | sub siblings { |
175 | my( $self ) = @_; |
176 | my $parent_col = $self->_parent_column; |
177 | my $primary_col = ($self->primary_columns())[0]; |
178 | my $rs = $self->result_source->resultset->search( |
179 | { |
180 | $parent_col => $self->get_column($parent_col), |
181 | $primary_col => { '!=' => $self->get_column($primary_col) }, |
182 | }, |
183 | ); |
184 | return $rs->all() if (wantarray()); |
185 | return $rs; |
186 | } |
187 | |
188 | =cut |
189 | |
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190 | =head2 attach_sibling |
191 | |
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192 | $obj->attach_sibling( $sibling ); |
193 | $obj->attach_sibling( $sibling, $sibling, ... ); |
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194 | |
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195 | Sets the passed in object(s) to have the same parent |
196 | as the calling object. Returns 1 on success and |
197 | 0 if the sibling already has the same parent. |
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198 | |
199 | =cut |
200 | |
201 | sub attach_sibling { |
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202 | my $self = shift; |
203 | my $return = 1; |
204 | foreach my $node (@_) { |
205 | $return = 0 if (!$node->parent( $self->parent() )); |
206 | } |
207 | return $return; |
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208 | } |
209 | |
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210 | =head2 is_leaf |
211 | |
212 | if ($obj->is_leaf()) { ... } |
213 | |
214 | Returns 1 if the object has no children, and 0 otherwise. |
215 | |
216 | =cut |
217 | |
218 | sub is_leaf { |
219 | my( $self ) = @_; |
220 | return $self->result_source->resultset->search( |
221 | { $self->_parent_column => $self->id() }, |
222 | { limit => 1 } |
223 | )->count(); |
224 | } |
225 | |
226 | =head2 is_root |
227 | |
228 | if ($obj->is_root()) { ... } |
229 | |
230 | Returns 1 if the object has no parent, and 0 otherwise. |
231 | |
232 | =cut |
233 | |
234 | sub is_root { |
235 | my( $self ) = @_; |
236 | return ( $self->get_column( $self->_parent_column ) ? 1 : 0 ); |
237 | } |
238 | |
239 | =head2 is_branch |
240 | |
241 | if ($obj->is_branch()) { ... } |
242 | |
243 | Returns 1 if the object has a parent and has children. |
244 | Returns 0 otherwise. |
245 | |
246 | =cut |
247 | |
248 | sub is_branch { |
249 | my( $self ) = @_; |
250 | return ( ($self->is_leaf() or $self->is_root()) ? 0 : 1 ); |
251 | } |
252 | |
253 | =head2 set_primary_key |
254 | |
255 | This method is an override of DBIx::Class' method for setting the |
256 | class' primary key column(s). This method passes control right on |
257 | to the normal method after first validating that only one column is |
258 | being selected as a primary key. If more than one column is then |
259 | an error will be thrown. |
260 | |
261 | =cut |
262 | |
263 | sub set_primary_ley { |
264 | my $self = shift; |
265 | if (@_>1) { |
266 | croak('You may only specify a single column as the primary key for adjacency tree classes'); |
267 | } |
268 | return $self->next::method( @_ ); |
269 | } |
270 | |
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271 | 1; |
272 | __END__ |
273 | |
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274 | =head1 INHERITED METHODS |
275 | |
276 | =head2 DBIx::Class |
277 | |
278 | =over 4 |
279 | |
280 | =item * |
281 | |
282 | L<mk_classdata|DBIx::Class/mk_classdata> |
283 | |
284 | =item * |
285 | |
286 | L<component_base_class|DBIx::Class/component_base_class> |
287 | |
288 | =back |
289 | |
290 | =head2 DBIx::Class::Componentised |
291 | |
292 | =over 4 |
293 | |
294 | =item * |
295 | |
296 | L<inject_base|DBIx::Class::Componentised/inject_base> |
297 | |
298 | =item * |
299 | |
300 | L<load_components|DBIx::Class::Componentised/load_components> |
301 | |
302 | =item * |
303 | |
304 | L<load_own_components|DBIx::Class::Componentised/load_own_components> |
305 | |
306 | =back |
307 | |
308 | =head2 Class::Data::Accessor |
309 | |
310 | =over 4 |
311 | |
312 | =item * |
313 | |
314 | L<mk_classaccessor|Class::Data::Accessor/mk_classaccessor> |
315 | |
316 | =back |
317 | |
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318 | =head1 AUTHOR |
319 | |
320 | Aran Clary Deltac <bluefeet@cpan.org> |
321 | |
322 | =head1 LICENSE |
323 | |
324 | You may distribute this code under the same terms as Perl itself. |
325 | |