Problem to set custom namespace when to try to spawn a robot on gazebo

[federicociresola]

Hi guys, while I was working on my project on ROS2 with Galatic version, I found a little problem while trying to set a custom namespace when calling the launch spawn_turtlebot3.launch.py for Gazebo. My aim is to set a custom namespace as the prefix on the topics published by the node of turtlebot3.

In the initial step, I tried to use the GroupAction to set the namespace through the method PushRosNamespace but it doesn't work in the correct way and I am still trying to figure out the why of this.

So I decided to modify the file and I added the following code:

• Add the new launch parameter here

  ns = LaunchConfiguration('ns',default='')

• and here

  dec_ns = DeclareLaunchArgument(
      'ns', 
      default_value   = '',
      description     = 'robot namespace')

• Add new parameter when the spawn Node is called, here:

  start_gazebo_ros_spawner_cmd = Node(
      package = 'gazebo_ros',
      executable = 'spawn_entity.py',
      arguments = [
          '-entity', model_robot,
          '-file', urdf_path,
          '-x', x_pose,
          '-y', y_pose,
          '-z', '0.01',
          '-robot_namespace', ns,
      ],
      output = 'screen',
  )

• Add the new parameter on LaunchDescription here:

  ld.add_action(dec_ns)

In this way, when somebody calls the launch file from CLI, or from another Launch file, the custom namespace can be set in easy way.

Is it normal that i have to go through all of these steps to achieve the result i want? Is there a better way to do this, which doesn't involve modifying the file in this repository? If there is not, maybe these changes can be included, maybe with a pull request by me? Thanks your understanding