ERROR: Cannot load message class for [my_examples_pkg/Age]. Are your messages built? Exercise 3.3

[akshay.ulavan]

I’m trying to solve the exercise 3.3 where I have to create a publisher to publish age of robot using custom message format. I followed the instructions to create the Age.msg and aslo added the necessary lines to CMakeLists.txt and package.xml.
When I start the node the topic can be seen in rostopic list and rostopic info as seen below.
But when I try to echo the topic I get an error:

user:~$ rostopic info /age_info
Type: my_examples_pkg/Age

Publishers:
 * /publish_age_node (http://9_xterm:33941/)

Subscribers: None


user:~$ rostopic echo /age_info
ERROR: Cannot load message class for [my_examples_pkg/Age]. Are your messages built?

[bayodesegun]

Hi @akshay.ulavan,

Welcome to the Community!

For solving this problem, please have a look at this post:

ERROR: Cannot load message class for [package/Message]. Are your messages built?

This error usually happens when you create a custom ROS message. SOLUTION: Please check the following in order. Painfully , #3 is a common and repeated cause, and it tends to happen even if you already know about it! Have you made the necessary and correct modifications to your CMakeLists.txt (and, where required, package.xml) file after creating the message file? You can find instructions on how to do this in the relevant section of the notebook describing how to create custo…

[akshay.ulavan]

Thanks @bayodesegun I am really enjoying the course

My issue was as mentioned in the post #3. I didn’t understand it the first time. But I realized that I hadn’t done source devel/setup.bash in shell 2 where I was running the command rostopic echo.

Thanks for the quick response!