NAME¶
Tangram::Type::Set::FromMany - maps Set::Object using a link table
SYNOPSIS¶
use Tangram;
# or
use Tangram::Core;
use Tangram::Type::Set::FromMany;
$schema = Tangram::Schema->new(
classes => { Company => { fields => {
set =>
{
# long form
employee =>
{
class => 'Person',
table => 'Company_employees',
coll => 'company',
item => 'employee',
},
# short form
assets => 'Asset',
}
DESCRIPTION¶
Maps a reference to a Set::Object. The persistent fields are grouped in a hash
under the "set" key in the field hash.
The set may contain only objects of persistent classes. These classes must have
a common persistent base class.
Tangram uses a link table to save the state of the collection. The table has two
columns: one contains the id of the container objects; the other contains the
ids of the elements.
The field names are passed in a hash that associates a field name with a field
descriptor. The field descriptor may be either a hash or a string. The hash
uses the following fields:
- * class
- * aggreg
- * table
- * coll
- * item
- * deep_update
Mandatory field "class" specifies the class of the elements.
Optional field "aggreg" specifies that the elements of the collection
must be removed (erased) from persistent storage along with the containing
object. The default is not to aggregate.
Optional field "table" sets the name of the link table. This defaults
to 'C_F', where C is the class of the containing object and F is the field
name.
Optional field "coll" sets the name the column containing the ids of
the containing objects. This defaults to 'coll'.
Optional field "item" sets the name the column containing the ids of
the elements. This defaults to 'item'.
Optional field "deep_update" specificies that all elements have to be
updated automatically when "update" is called on the collection
object. Automatic update ensures consisitency between the Perl representation
and the DBMS state, but degrades update performance so use it with caution.
The default is not to do automatic updates.
If the descriptor is a string, it is interpreted as the name of the element's
class. This is equivalent to specifying only the "class" field in
the hash variant.