NAME

       Tangram::Type::Set::FromOne - map Set::Object using a foreign key

SYNOPSIS

          use Tangram;

          # or
          use Tangram::Core;
          use Tangram::Type::Set::FromOne;

          $schema = Tangram::Schema->new(

             classes => { Basket => { fields => {

             iset =>
             {
                # long form
                fruits =>
                {
                   class => 'Fruit',
                   coll => 'basket',
                },

                # or (short form)
                fruits => 'Fruit',
             }

DESCRIPTION

       This class maps references to Set::Object collections in an intrusive fashion. The persistent fields are
       grouped in a hash under the "iset" 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 column on the element's table to store the id of the object containing the collection.

       CAUTION: the same object may not be an element of the same collection, in two different objects. This
       mapping may be used only for one-to-many relationships.

       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

           Mandatory field "class" specifies the class of the elements.

       •   aggreg

           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.

       •   back

           Optional field "back" sets the name of a field that is inserted in the elements. That field acts as a
           demand-loaded, read-only reference to the object containing the collection.

       •   coll

           Optional field "coll" sets the name the column containing the  id  of  the  containing  object.  This
           defaults  to  'C_m',  where  'C'  is  the  class  of the containing object (after passing through the
           normalisation function), and 'm' is the field name.

       •   deep_update

           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.

perl v5.36.0                                       2022-10-16                   Tangram::Type::Set::FromOne(3pm)