[SOLVED] Sending different Events via ZeroMQ using Flatbuffer Union

Sending different Events via ZeroMQ using Flatbuffer Union

I want to use flatbuffer to send events, which contain different data, over TCP (Using ZeroMQ). Therefore, I am using a Union.

// event.fbs
namespace event;

table ByteArray {
    bytes:[byte];
}

table OtherData {
    id:uint;
    value:uint;
}

union EventData {
    ByteArray,
    OtherData,
    String:string
}

table Event {
  name:string (key);
  timestamp:ulong = -1;
  data:EventData;
}

root_type Event;

In my C++-class I want to create new events and transfer them to my Publisher-class that sends out the events via ZeroMQ. Is there a nice or common way of doing this? I was thinking about something like this:

mPublisher.publishEvent(event::Event("event1", 0, "dataString"));
mPublisher.publishEvent(event::Event("event2", 1, byteArray));

The example above is not working because there is no such constructor. Is there a nice way of creating multiple events with different data? How am I supposed to pass these flatbuffer-events to another class like my publisher? Should I pass the flatbuffer or the event-offset?

Solution

You just need to use the actual constructors provided, so it will look something like:

event::CreateEvent(fbb, "event1", 0, fbb.CreateString("dataString"));

There is also an event::CreateByteArray etc. See the generated code, or the tutorial.

event::CreateEvent returns an offset into an unfinished FlatBuffer, so is generally not suitable for passing to non-FlatBuffer functions. You'll want to call fbb.Finish() on that offset, then pass the resulting buffer to other functions (again, see the tutorial).