[ros-users] callback function on one topic with different message types

[Jeremy Leibs]

http://www.ros.org/wiki/Topics

Ros topics are strongly typed, so in general what you are trying to do
won't work.  You must have a separate topic for each type.

The particular error you are seeing is related to the fact that a
subscription call is actually templated and infers the type of the
subscription based on the argument to your callback.

--Jeremy


On Tue, Mar 23, 2010 at 3:30 AM, Ugo Cupcic <ugo at shadowrobot.com> wrote:
> Hi all,
>
> I was wondering how I can achieve to have different callback functions
> on the same topic depending on the message types.
>
> Here is a small code that's not working :
>
> //msg type 1
> void myCallback(const shadowhand::msg1ConstPtr& msg)
> {
>   ROS_INFO("lapin1");
> }
>
> // msg type 2
> void myCallback(const shadowhand::msg2ConstPtr& msg)
> {
>   ROS_INFO("lapin2");
> }
>
> int main(int argc, char** argv)
> {
>   ros::init(argc, argv, "shadowhand_listener");
>   ros::NodeHandle n;
>   //subscribe to shadowhand_commands topic
>   ros::Subscriber chatter_sub = n.subscribe("shadowhand_commands",
> 100,                                                 myCallback);
>   ros::spin();
> }
>
>
>
> When I compile this code, I get the error:
> error: no matching function for call to
> ‘ros::NodeHandle::subscribe(const char [20], int, <unresolved overloaded
> function type>)’
>
> (If I comment the second callback, then it compiles fine).
>
> What am I doing wrong ?
>
> Cheers,
>
>
> Ugo
>
> --
> Ugo Cupcic         |  Shadow Robot Company | ugo at shadowrobot.com
> Software Engineer      251 Liverpool Road
> need a Hand?           London  N1 1LX       | +44 20 7700 2487
> http://www.shadowrobot.com/hand/              @shadowrobot
>
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