ros custom messages not adding to rosmsg list

Hello,

I am trying to use the ROS custom message support add-on, following the instructions. https://www.mathworks.com/help/ros/ug/ros-custom-message-support.html

I have run rosgenmsg inside my package, and it generates some files in matlab_gen that look like they contain my message structure.

E.g.

classdef carsimIn < robotics.ros.Message
    %carsimIn MATLAB implementation of Carsim_private_msgs/carsimIn
    %   This class was automatically generated by
    %   robotics.ros.msg.internal.gen.MessageClassGenerator.
    
    %   Copyright 2014-2020 The MathWorks, Inc.
    
    %#ok<*INUSD>
    
    properties (Constant)
        MessageType = 'Carsim_private_msgs/carsimIn' % The ROS message type
    end
    
    properties (Constant, Hidden)
        MD5Checksum = 'e026cbb8db5eb294079d0930d0ade4d3' % The MD5 Checksum of the message definition
    end
    
    properties (Access = protected)
        JavaMessage % The Java message object
    end
    
    properties (Constant, Access = protected)
        StdMsgsHeaderClass = robotics.ros.msg.internal.MessageFactory.getClassForType('std_msgs/Header') % Dispatch to MATLAB class for message type std_msgs/Header
    end
    
    properties (Dependent)
        Header
        Sender
        ThrottleCmd
        SteerCmd
        BrakeCmd
    end
    
    properties (Access = protected)
        Cache = struct('Header', []) % The cache for fast data access
    end
    
    properties (Constant, Hidden)
        PropertyList = {'BrakeCmd', 'Header', 'Sender', 'SteerCmd', 'ThrottleCmd'} % List of non-constant message properties
        ROSPropertyList = {'BrakeCmd', 'header', 'sender', 'SteerCmd', 'ThrottleCmd'} % List of non-constant ROS message properties
    end
    
    methods
        ...

I followed the three steps, and I can see with path and javaclasspath that both the java files and the message class files are a part of my paths.

However, when I run rosmsg list, my messages are no where to be found.

Answer 1

[Cam Salzberger]

Hello Jacob, I have a few suggested solutions and trouble-shooting steps here.

• Did you restart MATLAB? That is necessary to load new files from the Java path. It also refreshes the available ROS message list.
• Also, make sure that the folder structure is correct. MATLAB won't pick up message definitions that are nested under the expected top-level -> package -> msg/srv structure. In other words, it should look like:

% +top_level_folder/ - input to rosgenmsg
% |-+package_1/
% | '-+msg/
% |   '--MessageA.msg
% '-+package_2/
%   |-+msg/
%   | '--MessageB.msg
%   '-+srv/
%     '--ServiceC.srv

If neither of these work:

• Have you tried using the messages? Try both creating an empty message and sending/receiving with publisher/subscriber.
• Can you post the message definition? It looks pretty simple from what's autogenerated, but I want to see if they're matching.

-Cam