NAME

       UR::Singleton - Abstract class for implementing singleton objects

SYNOPSIS

         package MyApp::SomeClass;
         use UR;
         class MyApp::SomeClass {
             is => 'UR::Singleton',
             has => [
                 foo => { is => 'Number' },
             ]
         };

         $obj = MyApp::SomeClass->get();
         $obj->foo(1);

DESCRIPTION

       This class provides the infrastructure for singleton classes.  Singletons are classes of
       which there can only be one instance, and that instance's ID is the class name.

       If a class inherits from UR::Singleton, it overrides the default implementation of "get()"
       and "is_loaded()" in UR::Object with code that fabricates an appropriate object the first
       time it's needed.

       Singletons are most often used as one of the parent classes for data sources within a
       Namespace.  This makes it convienent to refer to them using only their name, as in a class
       definition.

METHODS

       _singleton_object
             $obj = Class::Name->_singleton_object;

             $obj = $obj->_singleton_object;

           Returns the object instance whether it is called as a class or object method.

       _singleton_class_name
             $class_name = Class::Name->_singleton_class_name;

             $class_name = $obj->_singleton_class_name;

           Returns the class name whether it is called as a class or object method.

SEE ALSO

       UR::Object