Error : Dot indexing is not supported for variables of this type. 【MATLAB ROS Unity】

Hello. I’m trying to do this tutorial for MATLAB Unity communication.

https://jp.mathworks.com/help/robotics/ug/pick-and-place-workflow-in-unity-3d-using-ros.html

But I got an error when I run this script.

helperConnectROSUnity;

Error message is below

Dot indexing is not supported for variables of this type.
Error in helperConnectROSUnity (line 16)
installPath = reg.getServiceInfo('unity_robotics_demo_msgs/SetModelConfiguration').installDir;

==Development environment==

OS：Windows10

MATLAB：R2022b

I cant find any solutions.

Any kind of help will be appreciated. Thank you.

Answer 1

[Hari Krishna Kakarla]

Hi MAKOTO,

Thanks for reaching out to us. To establish the connection between MATLAB and Unity, Instead of running the script helperConnectROSUnity, I suggest you to please run the following commands in MATLAB command window:

pyFile = ['"' fullfile(matlabroot,'sys','ros1',computer('arch'),...
    'ros1','lib','site-packages','ros_tcp_endpoint','default_server_endpoint.py') '"'];
pathToShellOrBATFile = ['"' fullfile(pwd,'unity_setup.bat') '"'];
execCmd = ['title ' 'UnitySetup' ' && ' pathToShellOrBATFile ' ' installPath ' ' pyFile '&'];
[status,msg] = ros.internal.runroscmd(execCmd);

The error message that you are getting currently is complaining about a custom message being not present. Creation of that custom messages is listed in the above steps in the example. But those all things may not be required for your case.

So, please just execute the above commands as I gave you above. That should work fine. Please let me know if you have any questions.

Thanks

Hari

[MAKOTO]

Thank you!

That work fine.

I just changed installPath such as.

'unity_robotics_demo_msgs/SetModelConfiguration'

Answer 2

[Walter Roberson]

reg.getServiceInfo('unity_robotics_demo_msgs/SetModelConfiguration') is returning empty -- you either did not involve the ROS support package or it did not get installed correctly.

[MAKOTO]

Thanks for your answer.

Isn’t it enough to install these three toolboxes?

• Robotics System Toolbox
• Stateflow
• ROS Toolbox

I just want to make sure helperConnectROSUnity; can be done.

Is there anything I should do?

[Walter Roberson]

It appears that there are a number of Unity related steps to set up as well. I am not willing to do those on my systems (not interested in getting an account with them for example.)

Meanwhile when I tried running the example, I got

Error using ros.internal.ROSEnvironment/createVenv

Unable to create Python virtual environment. System command returned: zsh:1: no matches found: /Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.9/bin/python*-config

.

Error in ros.internal.ROSEnvironment/checkAndCreateVenv (line 139)

createVenv(obj,pythonExe,venvRoot,rosVersion,...

Error in ros.internal.createOrGetLocalPython (line 52)

checkAndCreateVenv(rosEnv,'ros1',forceRecreateVenv);

Error in rosgenmsg (line 197)

ros.internal.createOrGetLocalPython(); %ensure python is available

and sure enough, there are no python*config files anywhere relevant under my /Library directory (MacOS) (There is one under /Library/Frameworks/Maple.framework which is for a different software package.)