ROS 2 Dynamic Typesupport Explanation

sgarciav · 2024-12-11T18:45:05.738Z

Hello all!

What am I trying to do?
I have a list of variables of different ROS types (specifically from a Behavior Tree blackboard, but this detail may be irrelevant). I want to save this list (blackboard) to a yaml or json file such that I can later read the file and create a new blackboard with the same data. To accomplish this I need to know the type of each variable in the list so the nodes can covert the data from json/yaml to its corresponding ROS data type.

I’ve been looking into ROS’s dynamic typesupport capabilities such that I can define a dynamic type and declare each variable in such a manner that my node can abstract the variables’ specific type. Specifically, I’m getting familiar with the ros2/rosidl_dynamic_typesupport repo. Unfortunately, I have not found documentation on how to use this tool.

In this post, @gbiggs made a reference to the osrf/dynamic_message_introspection package, but this does not seem to be what I’m looking for. (Please let me know if I’m mistaken).

Questions:
Is there documentation that I can study to better understand ROS’s dynamic typesupport capabilities? If not, can someone point me in the right direction?

Thank you all for your time and attention.

Sergio

ZhenshengLee · 2024-12-12T06:13:09.484Z

here for the basic concept of this, Internal ROS 2 interfaces — ROS 2 Documentation: Humble documentation

JM_ROS · 2024-12-12T13:07:39.878Z

Are you using C++ or pyhton ?
Also are your messages known / static in advance ?

sgarciav · 2024-12-13T14:41:05.315Z

I am using C++.

My messages are not known at compile time, only during runtime. The input list can be a combination of any data type depending on how the user sets up the behavior tree.

JM_ROS · 2024-12-17T10:17:33.074Z

In that case I am out of ideas. For static messages, there is a reflection API that you can use. This might work for dynamic messages as well, but the latest rumors I head about it was that its incomplete.

This is the reflection API in case you want to take a look:

github.com

rosidl/rosidl_typesupport_introspection_cpp at rolling · ros2/rosidl

Packages which provide the ROS IDL (.msg) definition and code generation. - ros2/rosidl