Callback Args in ROS2

Next Generation ROS
1

Hey All,

I was curious as to whether or not “callback_args” were going to make their way into ROS 2? If not, out of curiosity, what is the justification and are there any alternative solutions?

Thanks in advance.

1 Like
2

There’s no reason it could not be in rclpy. In C++, you’d probably just use a lambda or std::bind to accomplish this, but for convenience it could also be in rclcpp as well.

I would file a feature request issue on rclpy and/or rclcpp and consider doing a pr after getting feedback on the approach.

3

Thanks for the feedback and sorry for the delayed response. I haven’t filed a feature request yet but I did find a temporary fix. I was able to get similar functionality utilizing partial functions in python.

For example:

from functools import partial
create_subscription(msg_type, ros_topic, partial(callback_function, passed_variable))
3 Likes
4

Yeah, that’s a proper solution, similar to using a lambda or std::bind in C++. We’d only provide a similar interface in rclpy as a convenience, but it’s not necessary at all.

5

I’d vote for implementing it, at least in rclpy. I like to think of Python as a more beginner friendly interface many times.

@Seiwert thanks for your response anyways!