DataWriter Use Cases

Working with data writers.

Working with data writers.

Setting up a data writer

• Set up publisher
• Set up a topic
• Create a data writer, FooDataWriter, of user data type Foo:

  DDS_DataWriterQos writer_qos;
  DDS_ReturnCode_t retcode;
   
  // MyWriterListener is user defined and 
  // extends DDSDataWriterListener
  MyWriterListener* writer_listener = new MyWriterListener(); // or = NULL
   
  retcode = publisher->get_default_datawriter_qos(writer_qos);
   
  if (retcode != DDS_RETCODE_OK) {
      // ... error 
  }
   
  FooDataWriter* writer = publisher->create_datawriter(topic,
                                               writer_qos, 
                                               writer_listener,
                                                 DDS_STATUS_MASK_ALL);
  if (writer == NULL) {
      // ... error 
   
  };

Managing instances

• Getting an instance "key" value of user data type Foo

  Foo* data = ...;     // user data
   
  retcode = writer->get_key_value(*data, instance_handle);
   
  if (retcode != DDS_RETCODE_OK) {
      // ... check for cause of failure
  }    

• Registering an instance of type Foo

  DDS_InstanceHandle_t instance_handle = DDS_HANDLE_NIL;
   
  instance_handle = writer->register_instance(data); 

• Unregistering an instance of type Foo

  retcode = writer->unregister_instance(data, instance_handle);
   
  if (retcode != DDS_RETCODE_OK) {
      // ... check for cause of failure
  }  

• Disposing of an instance of type Foo

  retcode = writer->dispose(data, instance_handle);
   
  if (retcode != DDS_RETCODE_OK) {
      // ... check for cause of failure
  }  

Sending data

• Set up data writer
• Register instance
• Write instance of type Foo

  Foo* data;     // user data
   
  DDS_InstanceHandle_t instance_handle = 
                   DDS_HANDLE_NIL; // or a valid registered handle
   
  DDS_ReturnCode_t retcode;
   
  retcode = writer->write(data, instance_handle);
   
  if (retcode != DDS_RETCODE_OK) {
      // ... check for cause of failure
  }

Tearing down a data writer

• Delete DDSDataWriter:

  DDS_ReturnCode_t retcode;
   
  retcode = publisher->delete_datawriter(writer);
   
  if (retcode != DDS_RETCODE_OK) {
      // ... check for cause of failure
  }