1Rose::DB::Object::HelpeUrsse(r3)Contributed Perl DocumenRtoastei:o:nDB::Object::Helpers(3)
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NAME

6       Rose::DB::Object::Helpers - A mix-in class containing convenience
7       methods for Rose::DB::Object.
8

SYNOPSIS

10         package MyDBObject;
11
12         use Rose::DB::Object;
13         our @ISA = qw(Rose::DB::Object);
14
15         use Rose::DB::Object::Helpers 'clone',
16           { load_or_insert => 'find_or_create' };
17         ...
18
19         $obj = MyDBObject->new(id => 123);
20         $obj->find_or_create();
21
22         $obj2 = $obj->clone;
23

DESCRIPTION

25       Rose::DB::Object::Helpers provides convenience methods from use with
26       Rose::DB::Object-derived classes.  These methods do not exist in
27       Rose::DB::Object in order to keep the method namespace clean.  (Each
28       method added to Rose::DB::Object is another potential naming conflict
29       with a column accessor.)
30
31       This class inherits from Rose::Object::MixIn.  See the
32       Rose::Object::MixIn documentation for a full explanation of how to
33       import methods from this class.  The helper methods themselves are
34       described below.
35

FUNCTIONS VS. METHODS

37       Due to the "wonders" of Perl 5's object system, any helper method
38       described here can also be used as a Rose::DB::Object::Util-style
39       utility function that takes a Rose::DB::Object-derived object as its
40       first argument.  Example:
41
42         # Import two helpers
43         use Rose::DB::Object::Helpers qw(clone_and_reset traverse_depth_first);
44
45         $o = My::DB::Object->new(...);
46
47         clone_and_reset($o); # Imported helper "method" called as function
48
49         # Imported helper "method" with arguments called as function
50         traverse_depth_first($o, handlers => { ... }, max_depth => 2);
51
52       Why, then, the distinction between Rose::DB::Object::Helpers methods
53       and Rose::DB::Object::Util functions?  It's simply a matter of context.
54       The functions in Rose::DB::Object::Util are most useful in the context
55       of the internals (e.g., writing your own column method-maker) whereas
56       Rose::DB::Object::Helpers methods are most often added to a common
57       Rose::DB::Object-derived base class and then called as object methods
58       by all classes that inherit from it.
59
60       The point is, these are just conventions.  Use any of these subroutines
61       as functions or as methods as you see fit.  Just don't forget to pass a
62       Rose::DB::Object-derived object as the first argument when calling as a
63       function.
64

OBJECT METHODS

66   as_json [PARAMS]
67       Returns a JSON-formatted string created from the object tree as created
68       by the as_tree method.  PARAMS are the same as for the as_tree method,
69       except that the "deflate" parameter is ignored (it is always set to
70       true).
71
72       You must have the JSON module version 2.12 or later installed in order
73       to use this helper method.  If you have the JSON::XS module version
74       2.2222 or later installed, this method will work a lot faster.
75
76   as_tree [PARAMS]
77       Returns a reference to a hash of name/value pairs representing the
78       column values of this object as well as any nested sub-objects.  The
79       PARAMS name/value pairs dictate the details of the sub-object
80       traversal.  Valid parameters are:
81
82       allow_loops BOOL
83           If true, allow loops during the traversal (e.g., A -> B -> C -> A).
84           The default value is false.
85
86       deflate BOOL
87           If true, the values in the tree will be simple scalars suitable for
88           storage in the database (e.g., a date string like "2005-12-31"
89           instead of a DateTime object).  The default is true.
90
91       exclude CODEREF
92           A reference to a subroutine that is called on each
93           Rose::DB::Object-derived object encountered during the traversal.
94           It is passed the object, the parent object (undef, if none), and
95           the  Rose::DB::Object::Metadata::Relationship-derived object
96           (undef, if none) that led to this object.  If the subroutine
97           returns true, then this object is not processed.  Example:
98
99               exclude => sub
100               {
101                 my($object, $parent, $rel_meta) = @_;
102                 ...
103                 return 1  if($should_exclude);
104                 return 0;
105               },
106
107       force_load BOOL
108           If true, related sub-objects will be loaded from the database.  If
109           false, then only the sub-objects that have already been loaded from
110           the database will be traversed.  The default is false.
111
112       max_depth DEPTH
113           Do not descend past DEPTH levels.  Depth is an integer starting
114           from 0 for the object that the as_tree method was called on and
115           increasing with each level of related objects.  The default value
116           is 100.
117
118       persistent_columns_only BOOL
119           If true, non-persistent columns will not be included in the tree.
120           The default is false.
121
122       prune CODEREF
123           A reference to a subroutine that is called on each
124           Rose::DB::Object::Metadata::Relationship-derived object encountered
125           during traversal.  It is passed the relationship object, the parent
126           object, and the depth.  If the subroutine returns true, then the
127           entire sub-tree below this relationship will not be traversed.
128           Example:
129
130               prune => sub
131               {
132                 my($rel_meta, $object, $depth) = @_;
133                 ...
134                 return 1  if($should_prune);
135                 return 0;
136               },
137
138       Caveats: Currently, you cannot have a relationship and a column with
139       the same name in the same class.  This should not happen without
140       explicit action on the part of the class creator, but it is technically
141       possible.  The result of serializing such an object using as_tree is
142       undefined.  This limitation may be removed in the future.
143
144       The exact format of the "tree" data structure returned by this method
145       is not public and may change in the future (e.g., to overcome the
146       limitation described above).
147
148   as_yaml [PARAMS]
149       Returns a YAML-formatted string created from the object tree as created
150       by the as_tree method.  PARAMS are the same as for the as_tree method,
151       except that the "deflate" parameter is ignored (it is always set to
152       true).
153
154       You must have the YAML::Syck module installed in order to use this
155       helper method.
156
157   clone
158       Returns a new object initialized with the column values of the existing
159       object.  For example, imagine a "Person" class with three columns,
160       "id", "name", and "age".
161
162           $a = Person->new(id => 123, name => 'John', age => 30);
163
164       This use of the "clone()" method:
165
166           $b = $a->clone;
167
168       is equivalent to this:
169
170           $b = Person->new(id => $a->id, name => $a->name, age => $a->age);
171
172   clone_and_reset
173       This is the same as the clone method described above, except that it
174       also sets all of the primary and unique key columns to undef.  If the
175       cloned object has a db attribute, then it is copied to the clone object
176       as well.
177
178       For example, imagine a "Person" class with three columns, "id", "name",
179       and "age", where "id" is the primary key and "name" is a unique key.
180
181           $a = Person->new(id => 123, name => 'John', age => 30, db => $db);
182
183       This use of the "clone_and_reset()" method:
184
185           $b = $a->clone_and_reset;
186
187       is equivalent to this:
188
189           $b = Person->new(id => $a->id, name => $a->name, age => $a->age);
190           $b->id(undef);   # reset primary key
191           $b->name(undef); # reset unique key
192           $b->db($a->db);  # copy db
193
194   column_values_as_json
195       Returns a string containing a JSON representation of the object's
196       column values.  You must have the JSON module version 2.12 or later
197       installed in order to use this helper method.  If you have the JSON::XS
198       module version 2.2222 or later installed, this method will work a lot
199       faster.
200
201   column_values_as_yaml
202       Returns a string containing a YAML representation of the object's
203       column values.  You must have the YAML::Syck module installed in order
204       to use this helper method.
205
206   column_accessor_value_pairs
207       Returns a hash (in list context) or reference to a hash (in scalar
208       context) of column accessor method names and column values.  The keys
209       of the hash are the accessor method names for the columns.  The values
210       are retrieved by calling the accessor method for each column.
211
212   column_mutator_value_pairs
213       Returns a hash (in list context) or reference to a hash (in scalar
214       context) of column mutator method names and column values.  The keys of
215       the hash are the mutator method names for the columns.  The values are
216       retrieved by calling the accessor method for each column.
217
218   column_value_pairs
219       Returns a hash (in list context) or reference to a hash (in scalar
220       context) of column name and value pairs.  The keys of the hash are the
221       names of the columns.  The values are retrieved by calling the accessor
222       method for each column.
223
224   dirty_columns [ NAMES | COLUMNS ]
225       Given a list of column names or
226       Rose::DB::Object::Metadata::Column-derived objects, mark each column in
227       the invoking object as modifed.
228
229       If passed no arguments, returns a list of all modified columns in list
230       context or the number of modified columns in scalar context.
231
232   forget_related [ NAME | PARAMS ]
233       Given a foreign key or relationship name, forget any previously loaded
234       objects related by the specified foreign key or relationship.
235       Normally, any objects loaded by the default accessor methods for
236       relationships and foreign keys are fetched from the database only the
237       first time they are asked for, and simply returned thereafter.  Asking
238       them to be "forgotten" causes them to be fetched anew from the database
239       the next time they are asked for.
240
241       If the related object name is passed as a plain string NAME, then a
242       foreign key with that name is looked up.  If no such foreign key
243       exists, then a relationship with that name is looked up.  If no such
244       relationship or foreign key exists, a fatal error will occur.  Example:
245
246           $foo->forget_related('bar');
247
248       It's generally not a good idea to add a foreign key and a relationship
249       with the same name, but it is technically possible.  To specify the
250       domain of the name, pass the name as the value of a "foreign_key" or
251       "relationship" parameter.  Example:
252
253           $foo->forget_related(foreign_key => 'bar');
254           $foo->forget_related(relationship => 'bar');
255
256   has_loaded_related [ NAME | PARAMS ]
257       Given a foreign key or relationship name, return true if one or more
258       related objects have been loaded into the current object, false
259       otherwise.
260
261       If the name is passed as a plain string NAME, then a foreign key with
262       that name is looked up.  If no such foreign key exists, then a
263       relationship with that name is looked up.  If no such relationship or
264       foreign key exists, a fatal error will occur.  Example:
265
266           $foo->has_loaded_related('bar');
267
268       It's generally not a good idea to add a foreign key and a relationship
269       with the same name, but it is technically possible.  To specify the
270       domain of the name, pass the name as the value of a "foreign_key" or
271       "relationship" parameter.  Example:
272
273           $foo->has_loaded_related(foreign_key => 'bar');
274           $foo->has_loaded_related(relationship => 'bar');
275
276   init_with_column_value_pairs [ HASH | HASHREF ]
277       Initialize an object with a hash or reference to a hash of column/value
278       pairs.  This differs from the inherited init method in that it accepts
279       column names rather than method names.  A column name may not be the
280       same as its mutator method name if the column is aliased, for example.
281
282           $p = Person->new; # assume "type" column is aliased to "person_type"
283
284           # init() takes method/value pairs
285           $p->init(person_type => 'cool', age => 30);
286
287           # Helper takes a hashref of column/value pairs
288           $p->init_with_column_value_pairs({ type => 'cool', age => 30 });
289
290           # ...or a hash of column/value pairs
291           $p->init_with_column_value_pairs(type => 'cool', age => 30);
292
293   init_with_json JSON
294       Initialize the object with a JSON-formatted string.  The JSON string
295       must be in the format returned by the as_json (or
296       column_values_as_json) method.  Example:
297
298           $p1 = Person->new(name => 'John', age => 30);
299           $json = $p1->as_json;
300
301           $p2 = Person->new;
302           $p2->init_with_json($json);
303
304           print $p2->name; # John
305           print $p2->age;  # 30
306
307   init_with_deflated_tree TREE
308       This is the same as the init_with_tree method, except that it expects
309       all the values to be simple scalars suitable for storage in the
310       database (e.g., a date string like "2005-12-31" instead of a DateTime
311       object).  In other words, the TREE should be in the format generated by
312       the as_tree method called with the "deflate" parameter set to true.
313       Initializing objects in this way is slightly more efficient.
314
315   init_with_tree TREE
316       Initialize the object with a Perl data structure in the format returned
317       from the as_tree method.  Example:
318
319           $p1 = Person->new(name => 'John', age => 30);
320           $tree = $p1->as_tree;
321
322           $p2 = Person->new;
323           $p2->init_with_tree($tree);
324
325           print $p2->name; # John
326           print $p2->age;  # 30
327
328   init_with_yaml YAML
329       Initialize the object with a YAML-formatted string.  The YAML string
330       must be in the format returned by the as_yaml (or
331       column_values_as_yaml) method.  Example:
332
333           $p1 = Person->new(name => 'John', age => 30);
334           $yaml = $p1->as_yaml;
335
336           $p2 = Person->new;
337           $p2->init_with_yaml($yaml);
338
339           print $p2->name; # John
340           print $p2->age;  # 30
341
342   insert_or_update [PARAMS]
343       If the object already exists in the database, then update it.
344       Otherwise, insert it.  Any PARAMS are passed on to the call to save
345       (which is supplied with the appropriate "insert" or "update" boolean
346       parameter).
347
348       This method differs from the standard save method in that save decides
349       to insert or update based solely on whether or not the object was
350       previously loaded.  This method will take the extra step of actually
351       attempting to load the object to see whether or not it's in the
352       database.
353
354       The return value of the save method is returned.
355
356   insert_or_update_on_duplicate_key [PARAMS]
357       Update or insert a row with a single SQL statement, depending on
358       whether or not a row with the same primary or unique key already
359       exists.  Any PARAMS are passed on to the call to save (which is
360       supplied with the appropriate "insert" or "update" boolean parameter).
361
362       If the current database does not support the "ON DUPLICATE KEY UPDATE"
363       SQL extension, then this method simply calls the insert_or_update
364       method, passing all PARAMS.
365
366       Currently, the only database that supports "ON DUPLICATE KEY UPDATE" is
367       MySQL, and only in version 4.1.0 or later.  You can read more about the
368       feature here:
369
370       <http://dev.mysql.com/doc/refman/5.1/en/insert-on-duplicate.html>
371
372       Here's a quick example of the SQL syntax:
373
374           INSERT INTO table (a, b, c) VALUES (1, 2, 3)
375             ON DUPLICATE KEY UPDATE a = 1, b = 2, c = 3;
376
377       Note that there are two sets of columns and values in the statement.
378       This presents a choice: which columns to put in the "INSERT" part, and
379       which to put in the "UPDATE" part.
380
381       When using this method, if the object was previously loaded from the
382       database, then values for all columns are put in both the "INSERT" and
383       "UPDATE" portions of the statement.
384
385       Otherwise, all columns are included in both clauses except those
386       belonging to primary keys or unique keys which have only undefined
387       values.  This is important because it allows objects to be updated
388       based on a single primary or unique key, even if other possible keys
389       exist, but do not have values set.  For example, consider this table
390       with the following data:
391
392           CREATE TABLE parts
393           (
394             id      INT PRIMARY KEY,
395             code    CHAR(3) NOT NULL,
396             status  CHAR(1),
397
398             UNIQUE(code)
399           );
400
401           INSERT INTO parts (id, code, status) VALUES (1, 'abc', 'x');
402
403       This code will update part id 1, setting its "status" column to "y".
404
405           $p = Part->new(code => 'abc', status => 'y');
406           $p->insert_or_update_on_duplicate_key;
407
408       The resulting SQL:
409
410           INSERT INTO parts (code, status) VALUES ('abc', 'y')
411             ON DUPLICATE KEY UPDATE code = 'abc', status = 'y';
412
413       Note that the "id" column is omitted because it has an undefined value.
414       The SQL statement will detect the duplicate value for the unique key
415       "code" and then run the "UPDATE" portion of the query, setting "status"
416       to "y".
417
418       This method returns true if the row was inserted or updated
419       successfully, false otherwise.  The true value returned on success will
420       be the object itself.  If the object overloads its boolean value such
421       that it is not true, then a true value will be returned instead of the
422       object itself.
423
424       Yes, this method name is very long.  Remember that you can rename
425       methods on import.  It is expected that most people will want to rename
426       this method to "insert_or_update", using it in place of the normal
427       insert_or_update helper method:
428
429           package My::DB::Object;
430           ...
431           use Rose::DB::Object::Helpers
432             { insert_or_update_on_duplicate_key => 'insert_or_update' };
433
434   load_or_insert [PARAMS]
435       Try to load the object, passing PARAMS to the call to the load()
436       method.  The parameter "speculative => 1" is automatically added to
437       PARAMS.  If no such object is found, then the object is inserted.
438
439       Example:
440
441           # Get object id 123 if it exists, otherwise create it now.
442           $obj = MyDBObject->new(id => 123)->load_or_insert;
443
444   load_or_save [PARAMS]
445       Try to load the object, passing PARAMS to the call to the load()
446       method.  The parameter "speculative => 1" is automatically added to
447       PARAMS.  If no such object is found, then the object is saved.
448
449       This methods differs from load_or_insert in that the save method will
450       also save sub-objects.  See the documentation for Rose::DB::Object's
451       save method for more information.
452
453       Example:
454
455           @perms = (Permission->new(...), Permission->new(...));
456
457           # Get person id 123 if it exists, otherwise create it now
458           # along with permission sub-objects.
459           $person = Person->new(id => 123, perms => \@perms)->load_or_save;
460
461   load_speculative [PARAMS]
462       Try to load the object, passing PARAMS to the call to the load() method
463       along with the "speculative => 1" parameter.  See the documentation for
464       Rose::DB::Object's load method for more information.
465
466       Example:
467
468           $obj = MyDBObject->new(id => 123);
469
470           if($obj->load_speculative)
471           {
472             print "Found object id 123\n";
473           }
474           else
475           {
476             print "Object id 123 not found\n";
477           }
478
479   new_from_json JSON
480       The method is the equivalent of creating a new object and then calling
481       the init_with_json method on it, passing JSON as an argument.  See the
482       init_with_json method for more information.
483
484   new_from_deflated_tree TREE
485       The method is the equivalent of creating a new object and then calling
486       the init_with_deflated_tree method on it, passing TREE as an argument.
487       See the init_with_deflated_tree method for more information.
488
489   new_from_tree TREE
490       The method is the equivalent of creating a new object and then calling
491       the init_with_tree method on it, passing TREE as an argument.  See the
492       init_with_tree method for more information.
493
494   new_from_yaml YAML
495       The method is the equivalent of creating a new object and then calling
496       the init_with_yaml method on it, passing YAML as an argument.  See the
497       init_with_yaml method for more information.
498
499   strip [PARAMS]
500       This method prepares an object for serialization by stripping out
501       internal structures known to contain code references or other values
502       that do not survive serialization.  The object itself is returned, now
503       stripped.
504
505       Note: Operations that were scheduled to happen "on save()" will also be
506       stripped out by this method.  Examples include the databsae update or
507       insertion of any child objects attached to the parent object using
508       "get_set_on_save", "add_on_save", or "delete_on_save" methods.  If such
509       operations exist, an exception will be thrown unless the
510       "strip_on_save_ok" parameter is true.
511
512       If your object has these kinds of pending changes, either save() first
513       and then strip(), or clone() and then strip() the clone.
514
515       By default, the db object and all sub-objects (foreign keys or
516       relationships) are removed.  PARAMS are optional name/value pairs.
517       Valid PARAMS are:
518
519       leave [ NAME  | ARRAYREF ]
520           This parameter specifies which items to leave un-stripped.  The
521           value may be an item name or a reference to an array of item names.
522           Valid names are:
523
524           db  Do not remove the db object.  The db object will have its DBI
525               database handle (dbh) removed, however.
526
527           foreign_keys
528               Do not removed sub-objects that have already been loaded by
529               this object through foreign keys.
530
531           relationships
532               Do not removed sub-objects that have already been loaded by
533               this object through relationships.
534
535           related_objects
536               Do not remove any sub-objects (foreign keys or relationships)
537               that have already been loaded by this object.  This option is
538               the same as specifying both the "foreign_keys" and
539               "relationships" names.
540
541       strip_on_save_ok BOOL
542           If true, do not throw an exception when pending "on-save" changes
543           exist in the object; just strip them.  (See description above for
544           details.)
545
546   traverse_depth_first [ CODEREF | PARAMS ]
547       Do a depth-first traversal of the Rose::DB::Object-derived object that
548       this method is called on, descending into related objects. If a
549       reference to a subroutine is passed as the sole argument, it is taken
550       as the value of the "object" key to the "handlers" parameter hash (see
551       below).  Otherwise, PARAMS name/value pairs are expected.  Valid
552       parameters are:
553
554       allow_loops BOOL
555           If true, allow loops during the traversal (e.g., A -> B -> C -> A).
556           The default value is false.
557
558       context SCALAR
559           An arbitrary context variable to be passed along to (and possibly
560           modified by) each handler routine (see "handlers" parameter below).
561           The context may be any scalar value (e.g., an object, a reference
562           to a hash, etc.)
563
564       exclude CODEREF
565           A reference to a subroutine that is called on each
566           Rose::DB::Object-derived object encountered during the traversal.
567           It is passed the object, the parent object (undef, if none), and
568           the  Rose::DB::Object::Metadata::Relationship-derived object
569           (undef, if none) that led to this object.  If the subroutine
570           returns true, then this object is not processed.  Example:
571
572               exclude => sub
573               {
574                 my($object, $parent, $rel_meta) = @_;
575                 ...
576                 return 1  if($should_exclude);
577                 return 0;
578               },
579
580       force_load BOOL
581           If true, related sub-objects will be loaded from the database.  If
582           false, then only the sub-objects that have already been loaded from
583           the database will be traversed.  The default is false.
584
585       handlers HASHREF
586           A reference to a hash of handler subroutines.  Valid keys, calling
587           context, and the arguments passed to the referenced subroutines are
588           as follows.
589
590           object
591               This handler is called whenever a Rose::DB::Object-derived
592               object is encountered.  This includes the object that
593               traverse_depth_first was called on as well as any sub-objects.
594               The handler is passed the object, the "context", the parent
595               object (undef, if none), the
596               Rose::DB::Object::Metadata::Relationship-derived object through
597               which this object was arrived at (undef if none), and the
598               depth.
599
600               The handler must return the value to be used as the "context"
601               during the traversal of any related sub-objects.  The context
602               returned may be different than the context passed in.  Example:
603
604                   handlers =>
605                   {
606                     object => sub
607                     {
608                       my($object, $context, $parent, $rel_meta, $depth) = @_;
609                       ...
610
611                       return $context; # Important!
612                     }
613                     ...
614                   }
615
616           relationship
617               This handler is called just before a
618               Rose::DB::Object::Metadata::Relationship-derived object is
619               descended into  (i.e., just before the sub-objectes related
620               through this relationship are processed). The handler is passed
621               the object that contains the relationship, the "context", the
622               "context", and the relationship object itself.
623
624               The handler must return the value to be used as the "context"
625               during the traversal of the objects related through this
626               relationship.  (If you do not define this handler, then the
627               current context object will be used.)  The context returned may
628               be different than the context passed in.  Example:
629
630                   handlers =>
631                   {
632                     relationship => sub
633                     {
634                       my($object, $context, $rel_meta) = @_;
635                       ...
636
637                       return $context; # Important!
638                     }
639                     ...
640                   }
641
642           loop_avoided
643               This handler is called after the traversal refuses to process a
644               sub-object in order to avoid a loop.  (This only happens if the
645               "allow_loops" is parameter is false, obviously.)  The handler
646               is passed the object that was not processed, the "context", the
647               parent object, the previous "context", and the
648               Rose::DB::Object::Metadata::Relationship-derived object through
649               which the sub-object was related.  Example:
650
651                   handlers =>
652                   {
653                     loop_avoided => sub
654                     {
655                       my($object, $context, $parent, $prev_context, $rel_meta) = @_;
656                       ...
657                     }
658                     ...
659                   }
660
661       max_depth DEPTH
662           Do not descend past DEPTH levels.  Depth is an integer starting
663           from 0 for the object that the traverse_depth_first method was
664           called on and increasing with each level of related objects.  The
665           default value is 100.
666
667       prune CODEREF
668           A reference to a subroutine that is called on each
669           Rose::DB::Object::Metadata::Relationship-derived object encountered
670           during traversal.  It is passed the relationship object, the parent
671           object, and the depth.  If the subroutine returns true, then the
672           entire sub-tree below this relationship will not be traversed.
673           Example:
674
675               prune => sub
676               {
677                 my($rel_meta, $object, $depth) = @_;
678                 ...
679                 return 1  if($should_prune);
680                 return 0;
681               },
682

AUTHOR

684       John C. Siracusa (siracusa@gmail.com)
685

LICENSE

687       Copyright (c) 2010 by John C. Siracusa.  All rights reserved.  This
688       program is free software; you can redistribute it and/or modify it
689       under the same terms as Perl itself.
690
691
692
693perl v5.30.2                      2020-04-06      Rose::DB::Object::Helpers(3)
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