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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 | |
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12 | DBIx::Class::Tree::AdjacencyList - Manage a tree of data using the common adjacency list model. |
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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 | |
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34 | Optionally, automatically maintane a consistent tree structure. |
35 | |
36 | __PACKAGE__->repair_tree( 1 ); |
37 | |
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38 | Thats it, now you can modify and analyze the tree. |
39 | |
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40 | #!/usr/bin/perl |
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41 | use My::Employee; |
42 | |
43 | my $employee = My::Employee->create({ name=>'Matt S. Trout' }); |
44 | |
45 | my $rs = $employee->children(); |
46 | my @siblings = $employee->children(); |
47 | |
48 | my $parent = $employee->parent(); |
49 | $employee->parent( 7 ); |
50 | |
51 | =head1 DESCRIPTION |
52 | |
53 | This module provides methods for working with adjacency lists. The |
54 | adjacency list model is a very common way of representing a tree structure. |
55 | In this model each row in a table has a prent ID column that references the |
56 | primary key of another row in the same table. Because of this the primary |
57 | key must only be one column and is usually some sort of integer. The row |
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58 | with a parent ID of 0 is the root node and is usually the parent of all |
59 | other rows. Although, there is no limitation in this module that would |
60 | stop you from having multiple root nodes. |
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61 | |
62 | =head1 METHODS |
63 | |
64 | =head2 parent_column |
65 | |
66 | __PACKAGE__->parent_column('parent_id'); |
67 | |
68 | Declares the name of the column that contains the self-referential |
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69 | ID which defines the parent row. Defaults to "parent_id". This |
70 | will create a has_many (children) and belongs_to (parent) |
71 | relationship. |
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72 | |
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73 | This method also setups an additional has_many relationship called |
74 | parents which is useful when you want to treat an adjacency list |
75 | as a DAG. |
76 | |
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77 | =cut |
78 | |
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79 | __PACKAGE__->mk_classdata( '_parent_column' => 'parent_id' ); |
80 | |
81 | sub parent_column { |
82 | my $class = shift; |
83 | if (@_) { |
84 | my $parent_col = shift; |
85 | my $primary_col = ($class->primary_columns())[0]; |
86 | $class->belongs_to( '_parent' => $class => { "foreign.$primary_col" => "self.$parent_col" } ); |
87 | $class->has_many( 'children' => $class => { "foreign.$parent_col" => "self.$primary_col" } ); |
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88 | $class->has_many( 'parents' => $class => { "foreign.$primary_col" => "self.$parent_col" }, { cascade_delete => 0, cascade_copy => 0 } ); |
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89 | $class->_parent_column( $parent_col ); |
90 | return 1; |
91 | } |
92 | return $class->_parent_column(); |
93 | } |
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94 | |
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95 | =head2 repair_tree |
96 | |
97 | __PACKAGE__->repair_tree( 1 ); |
98 | |
99 | When set a true value this flag causes all changes to a node's parent to |
100 | trigger an integrity check on the tree. If, when changing a node's parent |
101 | to one of it's descendents then all its children will first be moved to have |
102 | the same current parent, and then the node's parent is changed. |
103 | |
104 | So, for example, if the tree is like this: |
105 | |
106 | A |
107 | B |
108 | C |
109 | D |
110 | E |
111 | F |
112 | |
113 | And you execute: |
114 | |
115 | $b->parent( $d ); |
116 | |
117 | Since D is a descendant of B then all of B's siblings get their parent |
118 | changed to A. Then B's parent is set to D. |
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119 | |
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120 | A |
121 | C |
122 | D |
123 | B |
124 | E |
125 | F |
126 | |
127 | =cut |
128 | |
129 | __PACKAGE__->mk_classdata( 'repair_tree' => 0 ); |
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130 | |
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131 | =head2 parent |
132 | |
133 | my $parent = $employee->parent(); |
134 | $employee->parent( $parent_obj ); |
135 | $employee->parent( $parent_id ); |
136 | |
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137 | Retrieves the object's parent object, or changes the object's |
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138 | parent to the specified parent or parent ID. If you would like |
139 | to make the object the root node, just set the parent to 0. |
140 | |
141 | If you are setting the parent then 0 will be returned if the |
142 | specified parent is already the object's parent and 1 on |
143 | success. |
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144 | |
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145 | =cut |
146 | |
147 | sub parent { |
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148 | my $self = shift; |
149 | if (@_) { |
150 | my $new_parent = shift; |
151 | my $parent_col = $self->_parent_column(); |
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152 | if (ref($new_parent)) { |
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153 | $new_parent = $new_parent->id() || croak('Parent object does not have an ID');; |
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154 | } |
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155 | return 0 if ($new_parent == ($self->get_column($parent_col)||0)); |
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156 | |
157 | if ($self->repair_tree()) { |
158 | my $found = $self->has_descendant( $new_parent ); |
159 | if ($found) { |
160 | my $children = $self->children(); |
161 | |
162 | while (my $child = $children->next()) { |
163 | $child->parent( $self->$parent_col() ); |
164 | } |
165 | } |
166 | } |
167 | |
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168 | $self->set_column( $parent_col => $new_parent ); |
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169 | $self->update(); |
170 | return 1; |
171 | } |
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172 | return $self->_parent(); |
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173 | } |
174 | |
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175 | =head2 has_descendant |
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176 | |
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177 | if ($employee->has_descendant( $id )) { ... } |
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178 | |
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179 | Returns true if the object has a descendant with the |
180 | specified ID. |
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181 | |
182 | =cut |
183 | |
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184 | sub has_descendant { |
185 | my ($self, $find_id) = @_; |
186 | |
187 | my $children = $self->children(); |
188 | while (my $child = $children->next()) { |
189 | if ($child->id() eq $find_id) { |
190 | return 1; |
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191 | } |
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192 | return 1 if ($child->has_descendant( $find_id )); |
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193 | } |
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194 | |
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195 | return 0; |
196 | } |
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197 | |
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198 | =head2 parents |
199 | |
200 | my $parents = $node->parents(); |
201 | my @parents = $node->parents(); |
202 | |
203 | This has_many relationship is not that useful as it will |
204 | never return more than one parent due to the one-to-many |
205 | structure of adjacency lists. The reason this relationship |
206 | is defined is so that this tree type may be treated as if |
207 | it was a DAG. |
208 | |
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209 | =head2 children |
210 | |
211 | my $children_rs = $employee->children(); |
212 | my @children = $employee->children(); |
213 | |
214 | Returns a list or record set, depending on context, of all |
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215 | the objects one level below the current one. This method |
216 | is created when parent_column() is called, which sets up a |
217 | has_many relationship called children. |
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218 | |
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219 | =head2 attach_child |
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220 | |
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221 | $parent->attach_child( $child ); |
222 | $parent->attach_child( $child, $child, ... ); |
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223 | |
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224 | Sets the child, or children, to the new parent. Returns 1 |
225 | on success and returns 0 if the parent object already has |
226 | the child. |
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227 | |
228 | =cut |
229 | |
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230 | sub attach_child { |
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231 | my $self = shift; |
232 | my $return = 1; |
233 | foreach my $child (@_) { |
234 | $child->parent( $self ); |
235 | } |
236 | return $return; |
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237 | } |
238 | |
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239 | =head2 siblings |
240 | |
241 | my $rs = $node->siblings(); |
242 | my @siblings = $node->siblings(); |
243 | |
244 | Returns either a result set or an array of all other objects |
245 | with the same parent as the calling object. |
246 | |
247 | =cut |
248 | |
249 | sub siblings { |
250 | my( $self ) = @_; |
251 | my $parent_col = $self->_parent_column; |
252 | my $primary_col = ($self->primary_columns())[0]; |
253 | my $rs = $self->result_source->resultset->search( |
254 | { |
255 | $parent_col => $self->get_column($parent_col), |
256 | $primary_col => { '!=' => $self->get_column($primary_col) }, |
257 | }, |
258 | ); |
259 | return $rs->all() if (wantarray()); |
260 | return $rs; |
261 | } |
262 | |
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263 | =head2 attach_sibling |
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264 | |
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265 | $obj->attach_sibling( $sibling ); |
266 | $obj->attach_sibling( $sibling, $sibling, ... ); |
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267 | |
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268 | Sets the passed in object(s) to have the same parent |
269 | as the calling object. Returns 1 on success and |
270 | 0 if the sibling already has the same parent. |
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271 | |
272 | =cut |
273 | |
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274 | sub attach_sibling { |
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275 | my $self = shift; |
276 | my $return = 1; |
277 | foreach my $node (@_) { |
278 | $return = 0 if (!$node->parent( $self->parent() )); |
279 | } |
280 | return $return; |
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281 | } |
282 | |
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283 | =head2 is_leaf |
284 | |
285 | if ($obj->is_leaf()) { ... } |
286 | |
287 | Returns 1 if the object has no children, and 0 otherwise. |
288 | |
289 | =cut |
290 | |
291 | sub is_leaf { |
292 | my( $self ) = @_; |
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293 | |
294 | my $has_child = $self->result_source->resultset->search( |
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295 | { $self->_parent_column => $self->id() }, |
296 | { limit => 1 } |
297 | )->count(); |
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298 | |
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299 | return $has_child ? 0 : 1; |
300 | } |
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301 | |
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302 | =head2 is_root |
303 | |
304 | if ($obj->is_root()) { ... } |
305 | |
306 | Returns 1 if the object has no parent, and 0 otherwise. |
307 | |
308 | =cut |
309 | |
310 | sub is_root { |
311 | my( $self ) = @_; |
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312 | return ( $self->get_column( $self->_parent_column ) ? 0 : 1 ); |
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313 | } |
314 | |
315 | =head2 is_branch |
316 | |
317 | if ($obj->is_branch()) { ... } |
318 | |
319 | Returns 1 if the object has a parent and has children. |
320 | Returns 0 otherwise. |
321 | |
322 | =cut |
323 | |
324 | sub is_branch { |
325 | my( $self ) = @_; |
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326 | return ( ($self->is_leaf() or $self->is_root()) ? 0 : 1 ); |
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327 | } |
328 | |
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329 | =head2 set_primary_key |
330 | |
331 | This method is an override of DBIx::Class' method for setting the |
332 | class' primary key column(s). This method passes control right on |
333 | to the normal method after first validating that only one column is |
334 | being selected as a primary key. If more than one column is then |
335 | an error will be thrown. |
336 | |
337 | =cut |
338 | |
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339 | sub set_primary_key { |
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340 | my $self = shift; |
341 | if (@_>1) { |
342 | croak('You may only specify a single column as the primary key for adjacency tree classes'); |
343 | } |
344 | return $self->next::method( @_ ); |
345 | } |
346 | |
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347 | 1; |
348 | __END__ |
349 | |
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350 | =head1 INHERITED METHODS |
351 | |
352 | =head2 DBIx::Class |
353 | |
354 | =over 4 |
355 | |
356 | =item * |
357 | |
358 | L<mk_classdata|DBIx::Class/mk_classdata> |
359 | |
360 | =item * |
361 | |
362 | L<component_base_class|DBIx::Class/component_base_class> |
363 | |
364 | =back |
365 | |
366 | =head2 DBIx::Class::Componentised |
367 | |
368 | =over 4 |
369 | |
370 | =item * |
371 | |
372 | L<inject_base|DBIx::Class::Componentised/inject_base> |
373 | |
374 | =item * |
375 | |
376 | L<load_components|DBIx::Class::Componentised/load_components> |
377 | |
378 | =item * |
379 | |
380 | L<load_own_components|DBIx::Class::Componentised/load_own_components> |
381 | |
382 | =back |
383 | |
384 | =head2 Class::Data::Accessor |
385 | |
386 | =over 4 |
387 | |
388 | =item * |
389 | |
390 | L<mk_classaccessor|Class::Data::Accessor/mk_classaccessor> |
391 | |
392 | =back |
393 | |
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394 | =head1 AUTHOR |
395 | |
396 | Aran Clary Deltac <bluefeet@cpan.org> |
397 | |
398 | =head1 LICENSE |
399 | |
400 | You may distribute this code under the same terms as Perl itself. |
401 | |