[actions] Describing the action client in more detail

Author: Murilo Marinho

docs/source/action_clients.rst

@@ -10,6 +10,7 @@ Action Clients
 TODO
 
 #. Create the Node with an :code:`ActionClient`.
+#. Update the :file:`setup.py` so that :program:`ros2 run` finds the node (if needed).
 
 :download:`move_straight_in_2d_action_client_node.py <../../ros2_tutorial_workspace/src/python_package_that_uses_the_actions/python_package_that_uses_the_actions/move_straight_in_2d_action_client_node.py>`
 

ros2_tutorial_workspace/src/python_package_that_uses_the_actions/python_package_that_uses_the_actions/move_straight_in_2d_action_client_node.py

@@ -23,7 +23,9 @@
 """
 import rclpy
 from rclpy.action import ActionClient
+from rclpy.action.client import ClientGoalHandle
 from rclpy.node import Node
+from rclpy.task import Future
 
 from geometry_msgs.msg import Point
 from package_with_interfaces.action import MoveStraightIn2D
@@ -33,37 +35,42 @@ class MoveStraightIn2DActionClientNode(Node):
 
     def __init__(self):
         super().__init__('move_straight_in_2d_action_client')
+
         self.action_client = ActionClient(self, MoveStraightIn2D, '/move_straight_in_2d')
 
-    def send_goal(self, desired_position: Point):
+        self.send_goal_future = None # This will be used in `send_goal`
+        self.get_result_future = None # This will be used in 'goal_response_callback'
+
+    def send_goal_async(self, desired_position: Point) -> None:
         goal_msg = MoveStraightIn2D.Goal()
         goal_msg.desired_position = desired_position
 
         while not self.action_client.wait_for_server(timeout_sec=1.0):
             self.get_logger().info(f'service {self.action_client} not available, waiting...')
 
+        self.get_logger().info(f'Sending goal: {desired_position}.')
+
         self.send_goal_future = self.action_client.send_goal_async(goal_msg, feedback_callback=self.action_feedback_callback)
         self.send_goal_future.add_done_callback(self.goal_response_callback)
 
-    def goal_response_callback(self, future):
-        goal_handle = future.result()
-        self.get_logger().info(f'The class of the future.result() is {goal_handle.__class__}')
+    def goal_response_callback(self, future: Future) -> None:
+        goal: ClientGoalHandle = future.result()
 
-        if not goal_handle.accepted:
+        if not goal.accepted:
             self.get_logger().info('Goal was rejected by the server.')
             return
         self.get_logger().info('Goal was accepted by the server.')
 
-        self.get_result_future = goal_handle.get_result_async()
+        self.get_result_future = goal.get_result_async()
         self.get_result_future.add_done_callback(self.action_result_callback)
 
-    def action_result_callback(self, future):
-        result = future.result().result
-        self.get_logger().info(f'Result: {result.final_position}')
+    def action_result_callback(self, future: Future) -> None:
+        response: MoveStraightIn2D.Response = future.result()
+        self.get_logger().info(f'Final position was: {response.result.final_position}.')
 
-    def action_feedback_callback(self, feedback_msg):
+    def action_feedback_callback(self, feedback_msg: MoveStraightIn2D.Feedback) -> None:
         feedback = feedback_msg.feedback
-        self.get_logger().info(f'Received feedback: {feedback.distance}')
+        self.get_logger().info(f'Received feedback distance: {feedback.distance}.')
 
 
 def main(args=None):
@@ -80,7 +87,7 @@ def main(args=None):
         desired_position = Point()
         desired_position.x = 1.0
         desired_position.y = -1.0
-        node.send_goal(desired_position)
+        node.send_goal_async(desired_position)
 
         rclpy.spin(node)
     except KeyboardInterrupt: