Import example code and basic prototype

launch/worlds/world_follow_target.launch.py

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+#!/usr/bin/env -S ros2 launch
+"""Launch worlds/follow_target.sdf and the required ROS<->IGN bridges"""
+
+from os import path
+from typing import List
+
+from ament_index_python.packages import get_package_share_directory
+from launch_ros.actions import Node
+from launch_ros.substitutions import FindPackageShare
+
+from launch import LaunchDescription
+from launch.actions import DeclareLaunchArgument, IncludeLaunchDescription
+from launch.launch_description_sources import PythonLaunchDescriptionSource
+from launch.substitutions import LaunchConfiguration, PathJoinSubstitution
+
+
+def generate_launch_description() -> LaunchDescription:
+
+    # Declare all launch arguments
+    declared_arguments = generate_declared_arguments()
+
+    # Get substitution for all arguments
+    world = LaunchConfiguration("world")
+    use_sim_time = LaunchConfiguration("use_sim_time")
+    ign_verbosity = LaunchConfiguration("ign_verbosity")
+    log_level = LaunchConfiguration("log_level")
+
+    # List of included launch descriptions
+    launch_descriptions = [
+        # Launch Ignition Gazebo
+        IncludeLaunchDescription(
+            PythonLaunchDescriptionSource(
+                PathJoinSubstitution(
+                    [
+                        FindPackageShare("ros_ign_gazebo"),
+                        "launch",
+                        "ign_gazebo.launch.py",
+                    ]
+                )
+            ),
+            launch_arguments=[("ign_args", [world, " -r -v ", ign_verbosity])],
+        ),
+    ]
+
+    # List of nodes to be launched
+    nodes = [
+        # ros_ign_bridge (clock -> ROS 2)
+        Node(
+            package="ros_ign_bridge",
+            executable="parameter_bridge",
+            output="log",
+            arguments=[
+                "/clock@rosgraph_msgs/msg/Clock[ignition.msgs.Clock",
+                "--ros-args",
+                "--log-level",
+                log_level,
+            ],
+            parameters=[{"use_sim_time": use_sim_time}],
+        ),
+        # ros_ign_bridge (target pose -> ROS 2)
+        Node(
+            package="ros_ign_bridge",
+            executable="parameter_bridge",
+            output="log",
+            arguments=[
+                "/model/target/pose"
+                + "@"
+                + "geometry_msgs/msg/PoseStamped[ignition.msgs.Pose",
+                "--ros-args",
+                "--log-level",
+                log_level,
+            ],
+            parameters=[{"use_sim_time": use_sim_time}],
+            remappings=[("/model/target/pose", "/target_pose")],
+        ),
+    ]
+
+    return LaunchDescription(declared_arguments + launch_descriptions + nodes)
+
+
+def generate_declared_arguments() -> List[DeclareLaunchArgument]:
+    """
+    Generate list of all launch arguments that are declared for this launch script.
+    """
+
+    return [
+        # World for Ignition Gazebo
+        DeclareLaunchArgument(
+            "world",
+            default_value=path.join(
+                get_package_share_directory("ign_moveit2_examples"),
+                "worlds",
+                "follow_target.sdf",
+            ),
+            description="Name or filepath of world to load.",
+        ),
+        # Miscellaneous
+        DeclareLaunchArgument(
+            "use_sim_time",
+            default_value="true",
+            description="If true, use simulated clock.",
+        ),
+        DeclareLaunchArgument(
+            "ign_verbosity",
+            default_value="2",
+            description="Verbosity level for Ignition Gazebo (0~4).",
+        ),
+        DeclareLaunchArgument(
+            "log_level",
+            default_value="warn",
+            description="The level of logging that is applied to all ROS 2 nodes launched by this script.",
+        ),
+    ]