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:

    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");
    }