[ros-users] How to identify the subscriber or the topic name related to a callback

[Jeremy Leibs]

On Tue, Feb 1, 2011 at 10:22 AM, Brian Gerkey <gerkey at willowgarage.com> wrote:
> On Mon, Jan 31, 2011 at 5:46 AM, Markus Bader <markus.bader at tuwien.ac.at> wrote:
>> I have multiple subscriber calling the same callback function. How can
>> I determinate within my callback function the related topic name?
>> getPublisherName gives me the related publisher but not the topic?
>
> hi Markus,
>
> At the time that you make the subscription, you can arrange for the
> topic to be passed into the callback, using boost::bind.  Appended
> below is a simple example that demonstrates this.

While Brian's recommendation certainly works, and is a useful pattern
for storing arbitrary data along with a generic callback, a different
approach is to use the "MessageEvent" callback signature instead.

http://www.ros.org/wiki/roscpp/Overview/Publishers%20and%20Subscribers#MessageEvent_.5BROS_1.1.2B-.5D

http://www.ros.org/doc/api/roscpp/html/classros_1_1MessageEvent.html

The connection_header is a std::map of std::strings, including keys,
"topic" and "callerid" among others.  This can be very useful for
getting more information about the context of your callback than just
the message.

--Jeremy