How to store ROS callback data in class properties?
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Alexandre Teixeira
on 3 Aug 2015
Commented: AYKUT SIRMA
on 26 Aug 2022
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!
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Accepted Answer
Sebastian Castro
on 3 Aug 2015
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
2 Comments
AYKUT SIRMA
on 26 Aug 2022
To receive only the Axes and Buttons data readings from 'sensor_msgs/Joy' message, what do I need to do? I try to write a callback function to get these 'sensor_msgs/Joy' to access Axes and Buttons information and put them into an array to use. I will be very glad if you would guide me, thank you very much.
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