oracular (3) Tangram::Type::Array::FromOne.3pm.gz

NAME

       Tangram::Type::Array::FromOne - map Perl arrays using a foreign key

SYNOPSIS

          use Tangram;

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

          $schema = Tangram::Schema->new(

             classes => { Agenda => { fields => {

             iarray =>
             {
                # long form
                entries =>
                {
                   class => 'Entry',
                   coll => 'agenda',
                },

                # or (short form)
                entries => 'Entry',
             }

DESCRIPTION

       This class maps references to a Perl array in an intrusive fashion. The persistent fields are grouped in
       a hash under the "iarray" key in the field hash.

       The array may contain only objects of persistent classes. These classes must have a common persistent
       base class.

       Tangram uses two columns on the element's table to store:

       •   the id of the object containing the collection

       •   the position of the element in 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

       •   aggreg

       •   back

       •   coll

       •   slot

       •   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 "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.

       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, and 'm' is the field name.

       Optional field "slot" sets the name the column containing the id of the containing object. This defaults
       to 'C_m_slot', where 'C' is the class of the containing object, and 'm' is the field name.

       The "C" in C_m and C_m_slot are passed through the schema normalisation function before being combined
       into a column name.

       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.