DataWriter Use Cases

Working with data writers. More...

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:

  DataWriterQos writer_qos = new DataWriterQos();
  DataWriterListener writer_listener = null;
  
  try {
      publisher.get_default_datawriter_qos(writer_qos);
  } catch (DDS.Exception) {
      Console.WriteLine(
          "***Error: failed to get default datawriter qos");
  }
  
  DataWriter writer = publisher.create_datawriter(topic, 
      writer_qos, 
      writer_listener,
      StatusMask.STATUS_MASK_NONE);
  if (writer == null) {
      Console.WriteLine("***Error: failed to create writer");
  }

Managing instances

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

  Foo data = ...;     // user data
  
  try {
      writer.get_key_value(data, ref instance_handle);
  } catch (DDS.Exception) {
      // ... check for cause of failure
  }    

• Registering an instance of type Foo

  InstanceHandle_t instance_handle = InstanceHandle_t.HANDLE_NIL;
  
  instance_handle = writer.register_instance(data); 

• Unregistering an instance of type Foo

  try {
      writer.unregister_instance(data, ref instance_handle);
  } catch (DDS.Exception) {
      // ... check for cause of failure
  }  

• Disposing of an instance of type Foo

  try {
      writer.dispose(data, ref instance_handle);
  } catch (DDS.Exception) {
      // ... check for cause of failure
  }  

Sending data

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

  Foo data = new Foo();     // user data
  InstanceHandle_t instance_handle =
      InstanceHandle_t.HANDLE_NIL; // or a valid registered handle
  
  try {
      writer.write(data, ref instance_handle);
  } catch (DDS.Exception) {
      Console.WriteLine("***Error: failed to write data");
  }

Tearing down a data writer

• Delete DataWriter:

  try {
      publisher.delete_datawriter(ref writer);
  } catch (DDS.Exception) {
      Console.WriteLine("***Error: failed to delete writer");
  }