Tangram::Type::Array::FromOne(3pm)			User Contributed Perl Documentation			Tangram::Type::Array::FromOne(3pm)

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 con-
       taining 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.

perl v5.8.8							    2006-03-29					Tangram::Type::Array::FromOne(3pm)