static function forceInstance(Singleton $object, $class = null)
	{
		if($class == null)
			$class = get_class($object);
		
		if(!isset(self::$instances[$class]))
		{
			self::$instances[$class] = $object;
		}
		else
		{
			throw new \Exception(sprintf('Object of class %s was previously instanciated', $class));
		}
	}