Working initializers

gistfile1.txt

return array(
    'invokables' => array(
      'db-class-one' => 'Application\Model\DbOne',
      'db-class-two' => 'Application\Model\DbTwo'
    ),
    'factories' => array(
        'Zend\Db\Adapter\Adapter' => 'Zend\Db\Adapter\AdapterServiceFactory'
    ),
    'initializers' => array( function($instance, $sm) {
        if ($instance instanceof \Application\Model\DBInterface) {
            $instance->setDbAdapter($sm->get('Zend\Db\Adapter\Adapter'));
        }
    })
)

// DbOne implements DbInterface

// Controller
$this->getServiceLocator()->get('db-class-one');