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Pubs / Subs by Hand

In addition to using the code generator, developers can implement publishers and subscribers manually through the lower-level API, which is always available.

warning

Units created by hand won't have the required metadata for use with deterministic replay.

Implementing a Publisher Manually​

To publish a message on the /chatter topic, you create a publisher by calling Advertise within the Unit:

my_publisher = Advertise<StringMessage>("/chatter");

Once the publisher is set up, you can publish a StringMessage like this:

std::shared_ptr<StringMessage> msg{std::make_shared<StringMessage>()};
msg->set_message(std::string("Hello, world!"));

my_publisher->Publish(msg);

Setting Up a Subscriber​

To set up a subscriber that listens to the /chatter topic, use the Subscribe function, which binds the incoming message to a callback method (in this case, MyUnit::OnChatter):

my_subscriber = Subscribe<StringMessage>("/chatter", std::bind(&MyUnit::OnChatter, this, _1));

The OnChatter callback method is defined with the following prototype:

MyUnit::OnChatter(std::shared_ptr<const StringMessage> msg) {
    // Process the incoming message
}

This method is invoked whenever a new message is received on the /chatter topic, allowing the Unit to process the incoming data.