MATLAB: How to store ROS callback data in class properties

robot operating systemros

Hello folks,
I am trying to store a callback data from ROS's topic called /scan in a properties (laser) of class that I created.
I got an error like this:
"No public field laser exists for class robotics.ros.Subscriber.
Error in MobileRobot/Callback_Laser (line 14) obj.laser = [message.Ranges];
Error in @(varargin)robot.Callback_Laser(varargin{:})
Error in robotics.ros.internal.onNewMessageCallback (line 44) feval(callbackFcn, source, message, userData{:});
Warning: Error occurred while evaluating listener callback."
Where is my mistake e how can I store a the callback data in a properties class?
Next the code class.
classdef MobileRobot < handle
  properties(Access = public)
      odom=[];
      laser = [];
  end
    methods(Access = public)
        function obj = MobileRobot()  % Constructor   
        end
        function  Callback_Laser(~, obj, message)
           % global laser
           % laser = [message.Ranges]; 
            obj.laser = [message.Ranges];
        end
    end
end
and the main code
 clear all;close all;clc;
 rosinit
 global rosMasterIp;
 rosMasterIp = 'http://192.168.0.113:11311';
 global localhostIp;
 localhostIp = '192.168.0.113';
 global robot;
 robot = MobileRobot();
 set_pose = robotics.ros.Node('getLaser',rosMasterIp,'NodeHost' , localhostIp);
 subs = rossubscriber('/scan',@robot.Callback_Laser);
Thank you!

Best Answer

The issue here seems to be that the callback tied to rossubscriber is required to have 2 inputs "src" and "msg", where "src" is the subscriber itself and "msg" is the message received.
Notice that the way you have defined your Callback_laser method, "obj" isn't the instance of the class, but rather a reference to the subscriber... which, as the error message suggests, does not have a "laser" property.
Does it work if you change your method to be the following?
function  Callback_Laser(obj, src, message) 
  obj.laser = [message.Ranges];
end
- Sebastian
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