Change feedback callback in ROS action client

Hi, I'm trying to define a ROS action client with customized callbacks.

The tutorial at the link https://it.mathworks.com/help/ros/ref/simpleactionclient.html works fine but I couldn't change the callbacks of the action client. I'm using the following code to initialize the action lib which, however, does not print anything when feedback messages are received.

action_name = '/fibonacci';

action_type = 'actionlib_tutorials/Fibonacci';

[actClient,goalMsg] = rosactionclient(action_name,action_type,'DataFormat','struct');

actClient.FeedbackFcn = @(~,msg)disp(['Feedback test: ',showDetailsAnyFormat(msg)])

If I comment out the last line, I can see the default print properly. I also tried to set the field actClient.FeedbackFcn equal to a different function handle but did not succeed.

Could you please help me understanding how to set the callbacks?

Thanks in advance!

Answer 1

[Maneet Kaur Bagga]

Hi Matina,

• As per my understanding, to set the callbacks for feedback messages a custom message subscriber using the "rossubscriber" function is created. The subscriber is set to listen to the "/fibonacci/feedback" topic, which is where the feedback messages are published for the "/fibonacci" action.
• Then define "customFeedbackCallback" function to handle the recieved feedback messages. This function will be called whenever a new feedback message is received.

Please refer to the code below:

action_name = '/fibonacci'; 
action_type = 'actionlib_tutorials/Fibonacci'; 

% Create an action client
[actClient, goalMsg] = rosactionclient(action_name, action_type, 'DataFormat', 'struct');

% Create a custom message subscriber for feedback messages
feedbackSub = rossubscriber('/fibonacci/feedback', 'actionlib_tutorials/FibonacciFeedback', @customFeedbackCallback);

% Start the action client
actClient.sendGoal(goalMsg);

% Define the custom feedback callback function
function customFeedbackCallback(~, msg)
    % Custom logic for handling feedback messages
    disp(['Custom Feedback: ', showDetailsAnyFormat(msg)]);
end

Please refer to the MATLAB Documentation for better understanding of the functions:

rossubscriber

https://www.mathworks.com/help/ros/ref/subscriber.html

rosactionclient

https://www.mathworks.com/help/ros/ref/simpleactionclient.html

Hope this helps!

Thank You!

Maneet Bagga