Topics¶

A topic is a subsection of a DDS Domain that enables exchange of data of a specific type, and that complies with certain restrictions on the exchange before exchange can occur.

A topic is identifiable by:

Name: Identifies the topic on the Domain. Must be unique on the Domain.
Quality of Service (optional): Determines the restrictions on the exchange. This is an optional parameter, which can be derived from fallbacks to the participant or defaults.
Type: The type of data being exchanged, which is the template parameter of the topic class:

Topics

template <typename T> class Topic {
...
// Constructor
        Topic(const dds::domain::DomainParticipant& dp,
                const std::string& name,
                const std::string& type_name,
                const dds::topic::qos::TopicQos& qos,
                dds::topic::TopicListener<T>* listener,
                const dds::core::status::StatusMask& mask);
...
}

Python code sample TBD

A topic is for exchanging data of the type Data_Type. The following shows how a topic is created on the DomainParticipant participant:

dds_entity_t topic = dds_create_topic (participant, &DataType_desc, "DataType", NULL, NULL);

dds::topic::Topic<Data_Type> topic(participant, "DataType Topic");

Python code sample TBD

To generate the data type of the topic from the user’s IDL files, use Cyclone DDS idlc generator (with the idlcxx library).

Important

Using types other than those generated from idlc + idlcxx in the template does not have the prerequisite traits, and therefore does not result in working code.