.. index:: Subscribers

.. _subscribers_bm:

===========
Subscribers
===========

A Subscriber is a consumer of data on a Domain. It uses the :ref:`domainparticipants_bm` 
to gain access to the Domain and is created using it. A Subscriber allows the 
:ref:`datareaders_bm` associated with it to share the same behaviour, such as:

- Liveliness notifications
- :ref:`qos_bm`
- :ref:`listeners_bm` callbacks

To use the default settings:

.. tabs::

    .. group-tab:: Core DDS (C)

      .. code-block:: C
			
			dds_entity_t subscriber = dds_create_subscriber (participant, NULL, NULL);

    .. group-tab:: C++

      .. code-block:: C++

			dds::sub::Subscriber sub(participant);

    .. group-tab:: Python

      .. code-block:: python

         subscriber = Subscriber(participant)

To supply your own settings:

.. tabs::

    .. group-tab:: Core DDS (C)

      .. code-block:: C

         dds_qos_t *qos = dds_create_qos ();
         dds_listener_t *listener = dds_create_listener(NULL);
         dds_lset_subscription_matched(listener, subscription_matched);
         dds_entity_t subscriber = dds_create_subscriber (participant, qos, listener);

    .. group-tab:: C++

      .. code-block:: C++

			dds::sub::NoOpSubscriberListener listener; /*you need to create your own class that derives from this listener, and implement your own callbacks*/
			/*the listener implementation should implement the on_subscription_matched virtual function as we will rely on it later*/
			dds::sub::qos::SubscriberQos subqos; /*add custom QoS policies that you want for this subscriber*/
			dds::sub::Subscriber sub(participant, subqos, &listener, dds::core::status::StatusMask::subscription_matched());

    .. group-tab:: Python

      .. code-block:: python

			Python code sample TBD

.. note::
	Any :ref:`datareaders_bm` created using ``sub`` inherit the qos and listener functionality as set through it.