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lib/DBIx/DataModel/Meta/Association.pm  view on Meta::CPAN

the path to the intermediate table, and the path from the intermediate
table to the remote end. Here is again the example from 
L<DBIx::DataModel/SYNOPSIS> : 

  My::Schema->define_association(
    kind => 'Association',
    A    => {
      table        => My::Schema::Department->metadm,
      role         => 'departments',
      multiplicity => '*',
      join_cols    => [qw/activities department/],
    },
    B    => {
      table        => My::Schema::Employee->metadm,
      role         => 'employees',
      multiplicity => '*',
      join_cols    => [qw/activities employee/],
    },
  );

=back

=item B

A description of the second I<association end>, following exactly the 
same principles as for the C<'A'> end.

=item name

Optional name for the association (otherwise an implicit name
will be built by default from the concatenation of the role names).

=item kind

A string describing the association kind, i.e. one of :
C<Association>, C<Aggregation> or C<Composition>.

Special behaviour is attached to the kind C<Composition> :

=over

=item *

the multiplicity must be 1-to-n or 1-to-0..1

=item * 

the C<'B'> end of the association (the "component" part) must not 
be component of another association (it can only be component of one
single composite table).

=item *

this association can be used for auto-expanding the composite object
(i.e. automatically fetching all component parts from the database)
-- see L<DBIx::DataModel::Source/expand>
and L<DBIx::DataModel::Source/auto_expand>

=item *

this association can be used for cascaded inserts like

  $source->insert({
    column1 => $val1,
    ...
    $component_name1 => [{$sub_object1}, ...],
    ...
   })

see L<DBIx::DataModel::Source/insert>


=back

=back


=head2 schema

returns the C<$meta_schema> to which this association belongs

=head2 A

hashref decribing the C<'A'> end of the association

=head2 B

hashref decribing the C<'B'> end of the association

=head2 path_AB

An instance of L<DBIx::DataModel::Meta::Path> for the path 
from C<A> to C<B> within this association (if any).

=head2 path_BA

An instance of L<DBIx::DataModel::Meta::Path> for the path 
from C<B> to C<A> within this association (if any).

=head2 name

The association name.

=head2 kind

The association kind.

=head1 PRIVATE METHODS

=head2 _parse_multiplicity

For multiplicities given as strings, parse into an arrayref 
C<< [$min, $max] >>, including the rules for shorthands
C<'*'> and C<'1'>, as described above.

=head2 _install_path

Implementation for regular associations (1-to-n or 1-to-1): 
create a L<DBIx::DataModel::Meta::Path> object from one side
to the other.