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Publisher

The |Publisher| acts on behalf of one or several |DataWriter| objects that belong to it. It serves as a container that allows grouping different DataWriter objects under a common configuration given by the |PublisherQos| of the Publisher.

DataWriter objects that belong to the same Publisher do not have any other relation among each other beyond the PublisherQos of the Publisher and act independently otherwise. Specifically, a Publisher can host DataWriter objects for different |Topics| and data types.

PublisherQos

|PublisherQos-api| controls the behavior of the |Publisher-api|. Internally it contains the following |QosPolicy-api| objects:

QosPolicy class Accessor/Mutator Mutable
|PresentationQosPolicy| |PublisherQos::presentation-api| Yes
|PartitionQosPolicy| |PublisherQos::partition-api| Yes
|GroupDataQosPolicy| |PublisherQos::group_data-api| Yes
|EntityFactoryQosPolicy| |PublisherQos::entity_factory-api| Yes

Refer to the detailed description of each |QosPolicy-api| class for more information about their usage and default values.

The QoS value of a previously created Publisher can be modified using the |Publisher::set_qos-api| member function.

.. literalinclude:: /../code/DDSCodeTester.cpp
   :language: c++
   :start-after: //DDS_CHANGE_PUBLISHERQOS
   :end-before: //!
   :dedent: 8

Default PublisherQos

The default :ref:`dds_layer_publisher_publisherQos` refers to the value returned by the |DomainParticipant::get_default_publisher_qos-api| member function on the DomainParticipant instance. The special value :class:`PUBLISHER_QOS_DEFAULT` can be used as QoS argument on |DomainParticipant::create_publisher-api| or |Publisher::set_qos-api| member functions to indicate that the current default PublisherQos should be used.

When the system starts, the default PublisherQos is equivalent to the default constructed value |PublisherQos::PublisherQos-api|. The default PublisherQos can be modified at any time using the |DomainParticipant::set_default_publisher_qos-api| member function on the :ref:`dds_layer_domainParticipant` instance. Modifying the default PublisherQos will not affect already existing :ref:`dds_layer_publisher_publisher` instances.

.. literalinclude:: /../code/DDSCodeTester.cpp
   :language: c++
   :start-after: //DDS_CHANGE_DEFAULT_PUBLISHERQOS
   :end-before: //!
   :dedent: 8

|DomainParticipant::set_default_publisher_qos-api| member function also accepts the special value PUBLISHER_QOS_DEFAULT as input argument. This will reset the current default PublisherQos to default constructed value |PublisherQos::PublisherQos-api|.

.. literalinclude:: /../code/DDSCodeTester.cpp
   :language: c++
   :start-after: //DDS_CHANGE_PUBLISHERQOS_TO_DEFAULT
   :end-before: //!
   :dedent: 8

Note

The value PUBLISHER_QOS_DEFAULT has different meaning depending on where it is used: