DataWriter Use Cases
[Programming How-To's]

Working with data writers. More...

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
    }