NAME

UMMF::Object::Extent - Traces the extent of objects.

SYNOPSIS

  my $extent = UMML::Object::Extent->new();

  # Begin tracing extents of UML::__ObjectBase.
  UML::__ObjectBase->add___extent($extent);

  ... Create some objects that are subclasses of UML::__ObjectBase ...

  # Select all objects where $object->isaAttribute is true.
  my @attributes = $extent->object_where(sub { shift->isaAttribute });

  UML::__ObjectBase->remove___extent($extent);

DESCRIPTION

Extents are used to capture and manipulate collections of objects in a particular context.

For example: object databases are extents because they capture objects that are stored in databases; a CGI application session is an extent because it captures objects (i.e. values) to be stored and retrieved.

This class provides a base class for extents.

Although this class captures creation of objects, it uses weak references such that captured objects are still subjected to garbage collection.

USAGE

EXPORT

None exported.

AUTHOR

Kurt Stephens, kstephens@users.sourceforge.net 2003/10/05

SEE ALSO

UMMF

VERSION

$Revision: 1.3 $

METHODS

add_object

  $extent->add_object($obj);

Called when a Classifier creates a new object.

This will assign an id, unique to this Extent. The id can be used to retrieve the object using <$extent-object_by_id($id)>>.

Returns the assigned id.

object_where

  my @obj = $extent->object_where($predicate);

Returns all $objects where <$predicate-($object)>> is true.

Any object that have been garbage-collected will not be selected.

object_by_id

  my $obj = $extent->object_by_id($id);

Returns the object stored in this Extent that was assigned the <$id>.

If the object has been garbage collected, this will return undef.