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1 | # vim: ts=8:sw=4:sts=4:et |
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2 | package DBIx::Class::Ordered; |
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3 | use strict; |
4 | use warnings; |
5 | use base qw( DBIx::Class ); |
6 | |
7 | =head1 NAME |
8 | |
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9 | DBIx::Class::Ordered - Modify the position of objects in an ordered list. |
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10 | |
11 | =head1 SYNOPSIS |
12 | |
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13 | Create a table for your ordered data. |
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14 | |
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15 | CREATE TABLE items ( |
16 | item_id INTEGER PRIMARY KEY AUTOINCREMENT, |
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17 | name TEXT NOT NULL, |
18 | position INTEGER NOT NULL |
19 | ); |
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20 | |
a8492531 |
21 | In your Schema or DB class add "Ordered" to the top |
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22 | of the component list. |
23 | |
a733c37f |
24 | __PACKAGE__->load_components(qw( Ordered ... )); |
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25 | |
26 | Specify the column that stores the position number for |
27 | each row. |
28 | |
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29 | package My::Item; |
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30 | __PACKAGE__->position_column('position'); |
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31 | |
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32 | That's it, now you can change the position of your objects. |
118e6b96 |
33 | |
34 | #!/use/bin/perl |
a733c37f |
35 | use My::Item; |
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36 | |
a733c37f |
37 | my $item = My::Item->create({ name=>'Matt S. Trout' }); |
38 | # If using grouping_column: |
39 | my $item = My::Item->create({ name=>'Matt S. Trout', group_id=>1 }); |
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40 | |
a733c37f |
41 | my $rs = $item->siblings(); |
42 | my @siblings = $item->siblings(); |
118e6b96 |
43 | |
44 | my $sibling; |
a733c37f |
45 | $sibling = $item->first_sibling(); |
46 | $sibling = $item->last_sibling(); |
47 | $sibling = $item->previous_sibling(); |
48 | $sibling = $item->next_sibling(); |
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49 | |
a733c37f |
50 | $item->move_previous(); |
51 | $item->move_next(); |
52 | $item->move_first(); |
53 | $item->move_last(); |
54 | $item->move_to( $position ); |
1d941d67 |
55 | $item->move_to_group( 'groupname' ); |
56 | $item->move_to_group( 'groupname', $position ); |
57 | $item->move_to_group( {group_id=>'groupname', 'other_group_id=>'othergroupname'} ); |
58 | $item->move_to_group( {group_id=>'groupname', 'other_group_id=>'othergroupname'}, $position ); |
118e6b96 |
59 | |
60 | =head1 DESCRIPTION |
61 | |
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62 | This module provides a simple interface for modifying the ordered |
63 | position of DBIx::Class objects. |
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64 | |
133dd22a |
65 | =head1 AUTO UPDATE |
66 | |
67 | All of the move_* methods automatically update the rows involved in |
68 | the query. This is not configurable and is due to the fact that if you |
69 | move a record it always causes other records in the list to be updated. |
70 | |
118e6b96 |
71 | =head1 METHODS |
72 | |
73 | =head2 position_column |
74 | |
75 | __PACKAGE__->position_column('position'); |
76 | |
77 | Sets and retrieves the name of the column that stores the |
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78 | positional value of each record. Defaults to "position". |
118e6b96 |
79 | |
80 | =cut |
81 | |
82 | __PACKAGE__->mk_classdata( 'position_column' => 'position' ); |
83 | |
a733c37f |
84 | =head2 grouping_column |
133dd22a |
85 | |
a733c37f |
86 | __PACKAGE__->grouping_column('group_id'); |
133dd22a |
87 | |
a8492531 |
88 | This method specifies a column to limit all queries in |
133dd22a |
89 | this module by. This effectively allows you to have multiple |
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90 | ordered lists within the same table. |
133dd22a |
91 | |
92 | =cut |
93 | |
a733c37f |
94 | __PACKAGE__->mk_classdata( 'grouping_column' ); |
133dd22a |
95 | |
118e6b96 |
96 | =head2 siblings |
97 | |
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98 | my $rs = $item->siblings(); |
99 | my @siblings = $item->siblings(); |
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100 | |
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101 | Returns either a resultset or an array of all other objects |
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102 | excluding the one you called it on. |
103 | |
104 | =cut |
105 | |
106 | sub siblings { |
107 | my( $self ) = @_; |
108 | my $position_column = $self->position_column; |
a9cdbec2 |
109 | my $rs = $self->result_source->resultset->search( |
7a76f44c |
110 | { |
111 | $position_column => { '!=' => $self->get_column($position_column) }, |
a733c37f |
112 | $self->_grouping_clause(), |
7a76f44c |
113 | }, |
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114 | { order_by => $self->position_column }, |
115 | ); |
7a76f44c |
116 | return $rs->all() if (wantarray()); |
117 | return $rs; |
118e6b96 |
118 | } |
119 | |
120 | =head2 first_sibling |
121 | |
a733c37f |
122 | my $sibling = $item->first_sibling(); |
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123 | |
5faa95af |
124 | Returns the first sibling object, or 0 if the first sibling |
a8492531 |
125 | is this sibling. |
118e6b96 |
126 | |
127 | =cut |
128 | |
129 | sub first_sibling { |
130 | my( $self ) = @_; |
5faa95af |
131 | return 0 if ($self->get_column($self->position_column())==1); |
fa6b598f |
132 | |
a9cdbec2 |
133 | return ($self->result_source->resultset->search( |
134 | { |
135 | $self->position_column => 1, |
a733c37f |
136 | $self->_grouping_clause(), |
a9cdbec2 |
137 | }, |
118e6b96 |
138 | )->all())[0]; |
139 | } |
140 | |
141 | =head2 last_sibling |
142 | |
a733c37f |
143 | my $sibling = $item->last_sibling(); |
118e6b96 |
144 | |
a8492531 |
145 | Returns the last sibling, or 0 if the last sibling is this |
5faa95af |
146 | sibling. |
118e6b96 |
147 | |
148 | =cut |
149 | |
150 | sub last_sibling { |
151 | my( $self ) = @_; |
a733c37f |
152 | my $count = $self->result_source->resultset->search({$self->_grouping_clause()})->count(); |
5faa95af |
153 | return 0 if ($self->get_column($self->position_column())==$count); |
a9cdbec2 |
154 | return ($self->result_source->resultset->search( |
155 | { |
156 | $self->position_column => $count, |
a733c37f |
157 | $self->_grouping_clause(), |
a9cdbec2 |
158 | }, |
118e6b96 |
159 | )->all())[0]; |
160 | } |
161 | |
162 | =head2 previous_sibling |
163 | |
a733c37f |
164 | my $sibling = $item->previous_sibling(); |
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165 | |
a8492531 |
166 | Returns the sibling that resides one position back. Returns undef |
167 | if the current object is the first one. |
118e6b96 |
168 | |
169 | =cut |
170 | |
171 | sub previous_sibling { |
172 | my( $self ) = @_; |
173 | my $position_column = $self->position_column; |
707cbb2d |
174 | my $position = $self->get_column( $position_column ); |
175 | return 0 if ($position==1); |
3ffca97b |
176 | return ($self->result_source->resultset->search( |
7a76f44c |
177 | { |
707cbb2d |
178 | $position_column => $position - 1, |
a733c37f |
179 | $self->_grouping_clause(), |
707cbb2d |
180 | } |
118e6b96 |
181 | )->all())[0]; |
182 | } |
183 | |
184 | =head2 next_sibling |
185 | |
a733c37f |
186 | my $sibling = $item->next_sibling(); |
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187 | |
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188 | Returns the sibling that resides one position forward. Returns undef |
189 | if the current object is the last one. |
118e6b96 |
190 | |
191 | =cut |
192 | |
193 | sub next_sibling { |
194 | my( $self ) = @_; |
195 | my $position_column = $self->position_column; |
707cbb2d |
196 | my $position = $self->get_column( $position_column ); |
a733c37f |
197 | my $count = $self->result_source->resultset->search({$self->_grouping_clause()})->count(); |
707cbb2d |
198 | return 0 if ($position==$count); |
133dd22a |
199 | return ($self->result_source->resultset->search( |
7a76f44c |
200 | { |
707cbb2d |
201 | $position_column => $position + 1, |
a733c37f |
202 | $self->_grouping_clause(), |
7a76f44c |
203 | }, |
118e6b96 |
204 | )->all())[0]; |
205 | } |
206 | |
80010e2b |
207 | =head2 move_previous |
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208 | |
a733c37f |
209 | $item->move_previous(); |
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210 | |
a8492531 |
211 | Swaps position with the sibling in the position previous in |
212 | the list. Returns 1 on success, and 0 if the object is |
213 | already the first one. |
118e6b96 |
214 | |
215 | =cut |
216 | |
80010e2b |
217 | sub move_previous { |
118e6b96 |
218 | my( $self ) = @_; |
133dd22a |
219 | my $position = $self->get_column( $self->position_column() ); |
220 | return $self->move_to( $position - 1 ); |
118e6b96 |
221 | } |
222 | |
80010e2b |
223 | =head2 move_next |
118e6b96 |
224 | |
a733c37f |
225 | $item->move_next(); |
118e6b96 |
226 | |
a8492531 |
227 | Swaps position with the sibling in the next position in the |
228 | list. Returns 1 on success, and 0 if the object is already |
229 | the last in the list. |
118e6b96 |
230 | |
231 | =cut |
232 | |
80010e2b |
233 | sub move_next { |
118e6b96 |
234 | my( $self ) = @_; |
133dd22a |
235 | my $position = $self->get_column( $self->position_column() ); |
a733c37f |
236 | my $count = $self->result_source->resultset->search({$self->_grouping_clause()})->count(); |
133dd22a |
237 | return 0 if ($position==$count); |
238 | return $self->move_to( $position + 1 ); |
118e6b96 |
239 | } |
240 | |
241 | =head2 move_first |
242 | |
a733c37f |
243 | $item->move_first(); |
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244 | |
a8492531 |
245 | Moves the object to the first position in the list. Returns 1 |
246 | on success, and 0 if the object is already the first. |
118e6b96 |
247 | |
248 | =cut |
249 | |
250 | sub move_first { |
251 | my( $self ) = @_; |
252 | return $self->move_to( 1 ); |
253 | } |
254 | |
255 | =head2 move_last |
256 | |
a733c37f |
257 | $item->move_last(); |
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258 | |
a8492531 |
259 | Moves the object to the last position in the list. Returns 1 |
260 | on success, and 0 if the object is already the last one. |
118e6b96 |
261 | |
262 | =cut |
263 | |
264 | sub move_last { |
265 | my( $self ) = @_; |
a733c37f |
266 | my $count = $self->result_source->resultset->search({$self->_grouping_clause()})->count(); |
118e6b96 |
267 | return $self->move_to( $count ); |
268 | } |
269 | |
270 | =head2 move_to |
271 | |
a733c37f |
272 | $item->move_to( $position ); |
118e6b96 |
273 | |
a8492531 |
274 | Moves the object to the specified position. Returns 1 on |
275 | success, and 0 if the object is already at the specified |
276 | position. |
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277 | |
278 | =cut |
279 | |
280 | sub move_to { |
281 | my( $self, $to_position ) = @_; |
282 | my $position_column = $self->position_column; |
283 | my $from_position = $self->get_column( $position_column ); |
133dd22a |
284 | return 0 if ( $to_position < 1 ); |
285 | return 0 if ( $from_position==$to_position ); |
dc66dea1 |
286 | my @between = ( |
287 | ( $from_position < $to_position ) |
288 | ? ( $from_position+1, $to_position ) |
289 | : ( $to_position, $from_position-1 ) |
290 | ); |
133dd22a |
291 | my $rs = $self->result_source->resultset->search({ |
dc66dea1 |
292 | $position_column => { -between => [ @between ] }, |
a733c37f |
293 | $self->_grouping_clause(), |
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294 | }); |
295 | my $op = ($from_position>$to_position) ? '+' : '-'; |
fa6b598f |
296 | $rs->update({ $position_column => \"$position_column $op 1" }); #" Sorry, GEdit bug |
79dc353a |
297 | $self->{_ORDERED_INTERNAL_UPDATE} = 1; |
b1c66eea |
298 | $self->update({ $position_column => $to_position }); |
118e6b96 |
299 | return 1; |
300 | } |
301 | |
fa6b598f |
302 | |
303 | |
79dc353a |
304 | =head2 move_to_group |
305 | |
306 | $item->move_to_group( $group, $position ); |
307 | |
308 | Moves the object to the specified position of the specified |
309 | group, or to the end of the group if $position is undef. |
310 | 1 is returned on success, and 0 is returned if the object is |
311 | already at the specified position of the specified group. |
312 | |
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313 | $group may be specified as a single scalar if only one |
314 | grouping column is in use, or as a hashref of column => value pairs |
315 | if multiple grouping columns are in use. |
fa6b598f |
316 | |
79dc353a |
317 | =cut |
318 | |
319 | sub move_to_group { |
320 | my( $self, $to_group, $to_position ) = @_; |
fa6b598f |
321 | |
322 | # if we're given a string, turn it into a hashref |
323 | unless (ref $to_group eq 'HASH') { |
324 | $to_group = {($self->_grouping_columns)[0] => $to_group}; |
325 | } |
326 | |
79dc353a |
327 | my $position_column = $self->position_column; |
fa6b598f |
328 | #my @grouping_columns = $self->_grouping_columns; |
79dc353a |
329 | |
330 | return 0 if ( ! defined($to_group) ); |
331 | return 0 if ( defined($to_position) and $to_position < 1 ); |
fa6b598f |
332 | return 0 if ( $self->_is_in_group($to_group) |
333 | and ((not defined($to_position)) |
334 | or (defined($to_position) and $self->$position_column==$to_position) |
335 | ) |
336 | ); |
79dc353a |
337 | |
338 | # Move to end of current group and adjust siblings |
339 | $self->move_last; |
340 | |
fa6b598f |
341 | $self->set_columns($to_group); |
79dc353a |
342 | my $new_group_count = $self->result_source->resultset->search({$self->_grouping_clause()})->count(); |
343 | if (!defined($to_position) or $to_position > $new_group_count) { |
344 | $self->{_ORDERED_INTERNAL_UPDATE} = 1; |
345 | $self->update({ $position_column => $new_group_count + 1 }); |
346 | } |
347 | else { |
348 | my @between = ($to_position, $new_group_count); |
349 | |
350 | my $rs = $self->result_source->resultset->search({ |
351 | $position_column => { -between => [ @between ] }, |
352 | $self->_grouping_clause(), |
353 | }); |
fa6b598f |
354 | $rs->update({ $position_column => \"$position_column + 1" }); #" |
79dc353a |
355 | $self->{_ORDERED_INTERNAL_UPDATE} = 1; |
356 | $self->update({ $position_column => $to_position }); |
357 | } |
358 | |
359 | return 1; |
360 | } |
361 | |
118e6b96 |
362 | =head2 insert |
363 | |
364 | Overrides the DBIC insert() method by providing a default |
365 | position number. The default will be the number of rows in |
366 | the table +1, thus positioning the new record at the last position. |
367 | |
368 | =cut |
369 | |
370 | sub insert { |
371 | my $self = shift; |
372 | my $position_column = $self->position_column; |
a733c37f |
373 | $self->set_column( $position_column => $self->result_source->resultset->search( {$self->_grouping_clause()} )->count()+1 ) |
118e6b96 |
374 | if (!$self->get_column($position_column)); |
0a298c73 |
375 | return $self->next::method( @_ ); |
118e6b96 |
376 | } |
377 | |
79dc353a |
378 | =head2 update |
379 | |
380 | Overrides the DBIC update() method by checking for a change |
381 | to the position and/or group columns. Movement within a |
382 | group or to another group is handled by repositioning |
383 | the appropriate siblings. Position defaults to the end |
384 | of a new group if it has been changed to undef. |
385 | |
386 | =cut |
387 | |
388 | sub update { |
389 | my $self = shift; |
390 | |
391 | if ($self->{_ORDERED_INTERNAL_UPDATE}) { |
392 | delete $self->{_ORDERED_INTERNAL_UPDATE}; |
393 | return $self->next::method( @_ ); |
394 | } |
395 | |
396 | $self->set_columns($_[0]) if @_ > 0; |
397 | my %changes = $self->get_dirty_columns; |
398 | $self->discard_changes; |
399 | |
400 | my $pos_col = $self->position_column; |
fa6b598f |
401 | |
fa6b598f |
402 | # if any of our grouping columns have been changed |
fa6b598f |
403 | if (grep {$_} map {exists $changes{$_}} $self->_grouping_columns ) { |
404 | |
405 | # create new_group by taking the current group and inserting changes |
406 | my $new_group = {$self->_grouping_clause}; |
407 | foreach my $col (keys %$new_group) { |
408 | if (exists $changes{$col}) { |
409 | $new_group->{$col} = $changes{$col}; |
410 | delete $changes{$col}; # don't want to pass this on to next::method |
411 | } |
412 | } |
413 | |
79dc353a |
414 | $self->move_to_group( |
fa6b598f |
415 | $new_group, |
79dc353a |
416 | exists($changes{$pos_col}) ? delete($changes{$pos_col}) : $self->$pos_col |
417 | ); |
418 | } |
419 | elsif (exists $changes{$pos_col}) { |
420 | $self->move_to(delete $changes{$pos_col}); |
421 | } |
422 | return $self->next::method( \%changes ); |
423 | } |
424 | |
118e6b96 |
425 | =head2 delete |
426 | |
427 | Overrides the DBIC delete() method by first moving the object |
428 | to the last position, then deleting it, thus ensuring the |
429 | integrity of the positions. |
430 | |
431 | =cut |
432 | |
433 | sub delete { |
434 | my $self = shift; |
435 | $self->move_last; |
0a298c73 |
436 | return $self->next::method( @_ ); |
118e6b96 |
437 | } |
438 | |
7a76f44c |
439 | =head1 PRIVATE METHODS |
440 | |
441 | These methods are used internally. You should never have the |
442 | need to use them. |
443 | |
a733c37f |
444 | =head2 _grouping_clause |
118e6b96 |
445 | |
a8492531 |
446 | This method returns a name=>value pair for limiting a search |
133dd22a |
447 | by the collection column. If the collection column is not |
448 | defined then this will return an empty list. |
118e6b96 |
449 | |
7a76f44c |
450 | =cut |
a733c37f |
451 | sub _grouping_clause { |
169bb185 |
452 | my( $self ) = @_; |
fa6b598f |
453 | return map { $_ => $self->get_column($_) } $self->_grouping_columns(); |
454 | } |
455 | |
456 | |
457 | |
458 | =head2 _get_grouping_columns |
459 | |
460 | Returns a list of the column names used for grouping, regardless of whether |
1d941d67 |
461 | they were specified as an arrayref or a single string, and returns () |
462 | if there is no grouping. |
fa6b598f |
463 | |
464 | =cut |
465 | sub _grouping_columns { |
466 | my( $self ) = @_; |
a733c37f |
467 | my $col = $self->grouping_column(); |
fa6b598f |
468 | if (ref $col eq 'ARRAY') { |
469 | return @$col; |
470 | } elsif ($col) { |
471 | return ( $col ); |
472 | } else { |
473 | return (); |
133dd22a |
474 | } |
7a76f44c |
475 | } |
476 | |
fa6b598f |
477 | |
478 | |
479 | =head2 _is_in_group($other) |
480 | |
481 | $item->_is_in_group( {user => 'fred', list => 'work'} ) |
482 | |
483 | Returns true if the object is in the group represented by hashref $other |
484 | =cut |
485 | sub _is_in_group { |
486 | my ($self, $other) = @_; |
487 | my $current = {$self->_grouping_clause}; |
488 | return 0 unless (ref $other eq 'HASH') and (keys %$current == keys %$other); |
489 | for my $key (keys %$current) { |
490 | return 0 unless exists $other->{$key}; |
491 | return 0 if $current->{$key} ne $other->{$key}; |
492 | } |
493 | return 1; |
494 | } |
495 | |
496 | |
7a76f44c |
497 | 1; |
498 | __END__ |
118e6b96 |
499 | |
500 | =head1 BUGS |
501 | |
dc66dea1 |
502 | =head2 Unique Constraints |
503 | |
504 | Unique indexes and constraints on the position column are not |
505 | supported at this time. It would be make sense to support them, |
506 | but there are some unexpected database issues that make this |
507 | hard to do. The main problem from the author's view is that |
508 | SQLite (the DB engine that we use for testing) does not support |
509 | ORDER BY on updates. |
510 | |
133dd22a |
511 | =head2 Race Condition on Insert |
512 | |
118e6b96 |
513 | If a position is not specified for an insert than a position |
514 | will be chosen based on COUNT(*)+1. But, it first selects the |
a8492531 |
515 | count, and then inserts the record. The space of time between select |
118e6b96 |
516 | and insert introduces a race condition. To fix this we need the |
517 | ability to lock tables in DBIC. I've added an entry in the TODO |
518 | about this. |
519 | |
133dd22a |
520 | =head2 Multiple Moves |
521 | |
522 | Be careful when issueing move_* methods to multiple objects. If |
523 | you've pre-loaded the objects then when you move one of the objects |
524 | the position of the other object will not reflect their new value |
525 | until you reload them from the database. |
526 | |
dc66dea1 |
527 | There are times when you will want to move objects as groups, such |
133dd22a |
528 | as changeing the parent of several objects at once - this directly |
529 | conflicts with this problem. One solution is for us to write a |
530 | ResultSet class that supports a parent() method, for example. Another |
531 | solution is to somehow automagically modify the objects that exist |
532 | in the current object's result set to have the new position value. |
533 | |
118e6b96 |
534 | =head1 AUTHOR |
535 | |
536 | Aran Deltac <bluefeet@cpan.org> |
537 | |
538 | =head1 LICENSE |
539 | |
540 | You may distribute this code under the same terms as Perl itself. |
541 | |