X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FDBIx%2FClass%2FRelationship.pm;h=d4926d187fb6a7cf3d35ae5731765b629bafa34e;hb=7f4433eb9bbe0650b4f5e2dff8bf817f4d28d3df;hp=39c0d12201e8a5985ebd5e114c61a5820ee43061;hpb=e951858e3c499abf50e7bbe7e1d4e57460825511;p=dbsrgits%2FDBIx-Class.git

diff --git a/lib/DBIx/Class/Relationship.pm b/lib/DBIx/Class/Relationship.pm
index 39c0d12..d4926d1 100644
--- a/lib/DBIx/Class/Relationship.pm
+++ b/lib/DBIx/Class/Relationship.pm
@@ -31,14 +31,17 @@ DBIx::Class::Relationship - Inter-table relationships
   MyDB::Schema::Actor->many_to_many('roles' => 'actorroles', 'role');
 
   ## Using relationships
-  $schema->resultset('Actor')->roles();
-  $schema->resultset('Role')->search_related('actors', { Name => 'Fred' });
-  $schema->resultset('ActorRole')->add_to_roles({ Name => 'Sherlock Holmes'});
+  $schema->resultset('Actor')->find({ id => 1})->roles();
+  $schema->resultset('Role')->find({ id => 1 })->actorroles->search_related('actor', { Name => 'Fred' });
+  $schema->resultset('Actor')->add_to_roles({ Name => 'Sherlock Holmes'});
 
 See L<DBIx::Class::Manual::Cookbook> for more.
 
 =head1 DESCRIPTION
 
+The word I<Relationship> has a specific meaning in DBIx::Class, see
+the definition in the L<Glossary|DBIx::Class::Manual::Glossary/Relationship>.
+
 This class provides methods to set up relationships between the tables
 in your database model. Relationships are the most useful and powerful
 technique that L<DBIx::Class> provides. To create efficient database queries,
@@ -102,29 +105,29 @@ L<DBIx::Class::Relationship::Base>.
 
 All helper methods are called similar to the following template:
 
-  __PACKAGE__->$method_name('relname', 'Foreign::Class', $cond, $attrs);
-  
+  __PACKAGE__->$method_name('relname', 'Foreign::Class', \%cond | \@cond, \%attrs);
+
 Both C<$cond> and C<$attrs> are optional. Pass C<undef> for C<$cond> if
-you want to use the default value for it, but still want to set C<$attrs>.
+you want to use the default value for it, but still want to set C<\%attrs>.
 
 See L<DBIx::Class::Relationship::Base> for documentation on the
-attrubutes that are allowed in the C<$attrs> argument.
+attributes that are allowed in the C<\%attrs> argument.
 
 
 =head2 belongs_to
 
 =over 4
 
-=item Arguments: $accessor_name, $related_class, $fk_column|\%cond|\@cond?, \%attr?
+=item Arguments: $accessor_name, $related_class, $our_fk_column|\%cond|\@cond?, \%attrs?
 
 =back
 
 Creates a relationship where the calling class stores the foreign
-class's primary key in one (or more) of its columns. This relationship
-defaults to using C<$accessor_name> as the column in this class
-to resolve the join against the primary key from C<$related_class>,
-unless C<$fk_column> specifies the foreign key column in this class or
-C<cond> specifies a reference to a join condition hash.
+class's primary key in one (or more) of the calling class columns.
+This relationship defaults to using C<$accessor_name> as the column
+name in this class to resolve the join against the primary key from
+C<$related_class>, unless C<$our_fk_column> specifies the foreign key column
+in this class or C<cond> specifies a reference to a join condition hash.
 
 =over
 
@@ -144,7 +147,7 @@ indicated by this relationship.
 This is the class name of the table referenced by the foreign key in
 this class.
 
-=item fk_column
+=item our_fk_column
 
 The column name on this class that contains the foreign key.
 
@@ -153,7 +156,7 @@ OR
 =item cond
 
 A hashref where the keys are C<foreign.$column_on_related_table> and
-the values are C<self.$foreign_key_column>. This is useful for
+the values are C<self.$our_fk_column>. This is useful for
 relations that are across multiple columns.
 
 =back
@@ -208,27 +211,34 @@ Cascading deletes are off by default on a C<belongs_to>
 relationship. To turn them on, pass C<< cascade_delete => 1 >>
 in the $attr hashref.
 
+By default, DBIC will return undef and avoid querying the database if a
+C<belongs_to> accessor is called when any part of the foreign key IS NULL. To
+disable this behavior, pass C<< undef_on_null_fk => 0 >> in the C<$attr>
+hashref.
+
 NOTE: If you are used to L<Class::DBI> relationships, this is the equivalent
 of C<has_a>.
 
 See L<DBIx::Class::Relationship::Base> for documentation on relationship
-methods and valid relationship attributes.
+methods and valid relationship attributes. Also see L<DBIx::Class::ResultSet>
+for a L<list of standard resultset attributes|DBIx::Class::ResultSet/ATTRIBUTES>
+which can be assigned to relationships as well.
 
 =head2 has_many
 
 =over 4
 
-=item Arguments: $accessor_name, $related_class, $foreign_key_column|\%cond|\@cond?, \%attr?
+=item Arguments: $accessor_name, $related_class, $their_fk_column|\%cond|\@cond?, \%attrs?
 
 =back
 
-Creates a one-to-many relationship, where the corresponding elements
-of the foreign class store the calling class's primary key in one (or
-more) of its columns. This relationship defaults to using the end of
-this classes namespace as the foreign key in C<$related_class> to
-resolve the join, unless C<$foreign_key_column> specifies the foreign
-key column in C<$related_class> or C<cond> specifies a reference to a
-join condition hash.
+Creates a one-to-many relationship where the foreign class refers to
+this class's primary key. This relationship refers to zero or more
+records in the foreign table (e.g. a C<LEFT JOIN>). This relationship 
+defaults to using the end of this classes namespace as the foreign key
+in C<$related_class> to resolve the join, unless C<$their_fk_column>
+specifies the foreign key column in C<$related_class> or C<cond>
+specifies a reference to a join condition hash.
 
 =over
 
@@ -249,7 +259,7 @@ indicated by this relationship.
 This is the class name of the table which contains a foreign key
 column containing PK values of this class.
 
-=item foreign_key_column
+=item their_fk_column
 
 The column name on the related class that contains the foreign key.
 
@@ -257,7 +267,7 @@ OR
 
 =item cond
 
-A hashref where the keys are C<foreign.$foreign_key_column> and
+A hashref where the keys are C<foreign.$their_fk_column> and
 the values are C<self.$matching_column>. This is useful for
 relations that are across multiple columns.
 
@@ -287,7 +297,7 @@ OR condition.
     'My::DBIC::Schema::Book', 
     { 'foreign.author_id' => 'self.id' },
   );
-  
+
   # OR (similar result, assuming related_class is storing our PK, in "author")
   # (the "author" is guessed at from "Author" in the class namespace)
   My::DBIC::Schema::Author->has_many(
@@ -330,9 +340,12 @@ L<DBIx::Class::Relationship::Base/"create_related">.
 
 If you delete an object in a class with a C<has_many> relationship, all
 the related objects will be deleted as well.  To turn this behaviour off,
-pass C<< cascade_delete => 0 >> in the C<attr> hashref. However, any
-database-level cascade or restrict will take precedence over a
-DBIx-Class-based cascading delete.
+pass C<< cascade_delete => 0 >> in the C<$attr> hashref.
+
+The cascaded operations are performed after the requested delete or
+update, so if your database has a constraint on the relationship, it
+will have deleted/updated the related records or raised an exception
+before DBIx::Class gets to perform the cascaded operation.
 
 If you copy an object in a class with a C<has_many> relationship, all
 the related objects will be copied as well. To turn this behaviour off,
@@ -340,19 +353,21 @@ pass C<< cascade_copy => 0 >> in the C<$attr> hashref. The behaviour
 defaults to C<< cascade_copy => 1 >>.
 
 See L<DBIx::Class::Relationship::Base> for documentation on relationship
-methods and valid relationship attributes.
+methods and valid relationship attributes. Also see L<DBIx::Class::ResultSet>
+for a L<list of standard resultset attributes|DBIx::Class::ResultSet/ATTRIBUTES>
+which can be assigned to relationships as well.
 
 =head2 might_have
 
 =over 4
 
-=item Arguments: $accessor_name, $related_class, $foreign_key_column|\%cond|\@cond?, \%attr?
+=item Arguments: $accessor_name, $related_class, $their_fk_column|\%cond|\@cond?, \%attrs?
 
 =back
 
 Creates an optional one-to-one relationship with a class. This relationship
 defaults to using C<$accessor_name> as the foreign key in C<$related_class> to
-resolve the join, unless C<$foreign_key_column> specifies the foreign key
+resolve the join, unless C<$their_fk_column> specifies the foreign key
 column in C<$related_class> or C<cond> specifies a reference to a join
 condition hash.
 
@@ -374,7 +389,7 @@ indicated by this relationship.
 This is the class name of the table which contains a foreign key
 column containing PK values of this class.
 
-=item foreign_key_column
+=item their_fk_column
 
 The column name on the related class that contains the foreign key.
 
@@ -382,8 +397,8 @@ OR
 
 =item cond
 
-A hashref where the keys are C<foreign.$column_on_related_table> and
-the values are C<self.$foreign_key_column>. This is useful for
+A hashref where the keys are C<foreign.$their_fk_column> and
+the values are C<self.$matching_column>. This is useful for
 relations that are across multiple columns.
 
 =back
@@ -414,23 +429,40 @@ relations that are across multiple columns.
 If you update or delete an object in a class with a C<might_have>
 relationship, the related object will be updated or deleted as well. To
 turn off this behavior, add C<< cascade_delete => 0 >> to the C<$attr>
-hashref. Any database-level update or delete constraints will override
-this behavior.
+hashref.
+
+The cascaded operations are performed after the requested delete or
+update, so if your database has a constraint on the relationship, it
+will have deleted/updated the related records or raised an exception
+before DBIx::Class gets to perform the cascaded operation.
 
 See L<DBIx::Class::Relationship::Base> for documentation on relationship
-methods and valid relationship attributes.
+methods and valid relationship attributes. Also see L<DBIx::Class::ResultSet>
+for a L<list of standard resultset attributes|DBIx::Class::ResultSet/ATTRIBUTES>
+which can be assigned to relationships as well.
+
+Note that if you supply a condition on which to join, if the column in the
+current table allows nulls (i.e., has the C<is_nullable> attribute set to a
+true value), than C<might_have> will warn about this because it's naughty and
+you shouldn't do that.  
+
+ "might_have/has_one" must not be on columns with is_nullable set to true (MySchema::SomeClass/key)
+
+If you must be naughty, you can suppress the warning by setting
+C<DBIC_DONT_VALIDATE_RELS> environment variable to a true value.  Otherwise,
+you probably just want to use C<DBIx::Class::Relationship/belongs_to>.
 
 =head2 has_one
 
 =over 4
 
-=item Arguments: $accessor_name, $related_class, $foreign_key_column|\%cond|\@cond?, \%attr?
+=item Arguments: $accessor_name, $related_class, $their_fk_column|\%cond|\@cond?, \%attrs?
 
 =back
 
 Creates a one-to-one relationship with a class. This relationship
 defaults to using C<$accessor_name> as the foreign key in C<$related_class> to
-resolve the join, unless C<$foreign_key_column> specifies the foreign key
+resolve the join, unless C<$their_fk_column> specifies the foreign key
 column in C<$related_class> or C<cond> specifies a reference to a join
 condition hash.
 
@@ -452,7 +484,7 @@ indicated by this relationship.
 This is the class name of the table which contains a foreign key
 column containing PK values of this class.
 
-=item foreign_key_column
+=item their_fk_column
 
 The column name on the related class that contains the foreign key.
 
@@ -460,8 +492,8 @@ OR
 
 =item cond
 
-A hashref where the keys are C<foreign.$column_on_related_table> and
-the values are C<self.$foreign_key_column>. This is useful for
+A hashref where the keys are C<foreign.$their_fk_column> and
+the values are C<self.$matching_column>. This is useful for
 relations that are across multiple columns.
 
 =back
@@ -503,16 +535,27 @@ In the above example, each Book in the database is associated with exactly one
 ISBN object.
 
 See L<DBIx::Class::Relationship::Base> for documentation on relationship
-methods and valid relationship attributes.
+methods and valid relationship attributes. Also see L<DBIx::Class::ResultSet>
+for a L<list of standard resultset attributes|DBIx::Class::ResultSet/ATTRIBUTES>
+which can be assigned to relationships as well.
+
+Note that if you supply a condition on which to join, if the column in the
+current table allows nulls (i.e., has the C<is_nullable> attribute set to a
+true value), than warnings might apply just as with
+L<DBIx::Class::Relationship/might_have>.
 
 =head2 many_to_many
 
 =over 4
 
-=item Arguments: $accessor_name, $link_rel_name, $foreign_rel_name, \%attr?
+=item Arguments: $accessor_name, $link_rel_name, $foreign_rel_name, \%attrs?
 
 =back
 
+C<many_to_many> is a I<Relationship bridge> which has a specific
+meaning in DBIx::Class, see the definition in the
+L<Glossary|DBIx::Class::Manual::Glossary/Relationship bridge>.
+
 C<many_to_many> is not strictly a relationship in its own right. Instead, it is
 a bridge between two resultsets which provide the same kind of convenience
 accessors as true relationships provide. Although the accessor will return a 
@@ -586,7 +629,9 @@ will be created for the Role class for the C<actors> many_to_many
 relationship.
 
 See L<DBIx::Class::Relationship::Base> for documentation on relationship
-methods and valid relationship attributes.
+methods and valid relationship attributes. Also see L<DBIx::Class::ResultSet>
+for a L<list of standard resultset attributes|DBIx::Class::ResultSet/ATTRIBUTES>
+which can be assigned to relationships as well.
 
 =cut