Use const& signature for read-only sub callbacks (#2297)

The constant reference message signatures should be preferred over the shared pointer to constant message signatures for read-only subscriber callbacks, as discussed in ros2/rclcpp#1598. As such, it makes sense to migrate to said signatures in documentation. Signed-off-by: Abrar Rahman Protyasha <[email protected]> (cherry picked from commit e4cd3cb) # Conflicts: # source/Tutorials/Custom-ROS2-Interfaces.rst # source/Tutorials/FastDDS-Configuration/FastDDS-Configuration.rst # source/Tutorials/Tf2/Writing-A-Tf2-Broadcaster-Cpp.rst # source/Tutorials/Writing-A-Simple-Cpp-Publisher-And-Subscriber.rst
ros2 · Feb 9, 2022 · 4275c66 · 4275c66
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diff --git a/source/Tutorials/Custom-ROS2-Interfaces.rst b/source/Tutorials/Custom-ROS2-Interfaces.rst
@@ -325,9 +325,13 @@ Subscriber:
         }
 
       private:
+<<<<<<< HEAD
         void topic_callback(const tutorial_interfaces::msg::Num::SharedPtr msg) const  // CHANGE
+=======
+        void topic_callback(const tutorial_interfaces::msg::Num & msg) const  // CHANGE
+>>>>>>> e4cd3cb (Use `const&` signature for read-only sub callbacks (#2297))
         {
-          RCLCPP_INFO_STREAM(this->get_logger(), "I heard: '" << msg->num << "'");     // CHANGE
+          RCLCPP_INFO_STREAM(this->get_logger(), "I heard: '" << msg.num << "'");     // CHANGE
         }
         rclcpp::Subscription<tutorial_interfaces::msg::Num>::SharedPtr subscription_;  // CHANGE
       };

diff --git a/source/Tutorials/FastDDS-Configuration/FastDDS-Configuration.rst b/source/Tutorials/FastDDS-Configuration/FastDDS-Configuration.rst
@@ -347,9 +347,13 @@ In a new source file named ``src/sync_async_reader.cpp`` write the following con
         /**
          * Actions to run every time a new message is received
          */
+<<<<<<< HEAD
         void topic_callback(const std_msgs::msg::String::SharedPtr msg) const
+=======
+        void topic_callback(const std_msgs::msg::String & msg) const
+>>>>>>> e4cd3cb (Use `const&` signature for read-only sub callbacks (#2297))
         {
-            RCLCPP_INFO(this->get_logger(), "I heard: '%s'", msg->data.c_str());
+            RCLCPP_INFO(this->get_logger(), "I heard: '%s'", msg.data.c_str());
         }
 
         // A subscriber that listens to topic 'sync_topic'

diff --git a/source/Tutorials/Tf2/Writing-A-Tf2-Broadcaster-Cpp.rst b/source/Tutorials/Tf2/Writing-A-Tf2-Broadcaster-Cpp.rst
@@ -106,7 +106,11 @@ Open the file using your preferred text editor.
      }
 
    private:
+<<<<<<< HEAD
      void handle_turtle_pose(const std::shared_ptr<turtlesim::msg::Pose> msg)
+=======
+     void handle_turtle_pose(const turtlesim::msg::Pose & msg)
+>>>>>>> e4cd3cb (Use `const&` signature for read-only sub callbacks (#2297))
      {
        rclcpp::Time now = this->get_clock()->now();
        geometry_msgs::msg::TransformStamped t;
@@ -119,15 +123,15 @@ Open the file using your preferred text editor.
 
        // Turtle only exists in 2D, thus we get x and y translation
        // coordinates from the message and set the z coordinate to 0
-       t.transform.translation.x = msg->x;
-       t.transform.translation.y = msg->y;
+       t.transform.translation.x = msg.x;
+       t.transform.translation.y = msg.y;
        t.transform.translation.z = 0.0;
 
        // For the same reason, turtle can only rotate around one axis
        // and this why we set rotation in x and y to 0 and obtain
        // rotation in z axis from the message
        tf2::Quaternion q;
-       q.setRPY(0, 0, msg->theta);
+       q.setRPY(0, 0, msg.theta);
        t.transform.rotation.x = q.x();
        t.transform.rotation.y = q.y();
        t.transform.rotation.z = q.z();
@@ -195,15 +199,15 @@ Here we copy the information from the 3D turtle pose into the 3D transform.
 
     // Turtle only exists in 2D, thus we get x and y translation
     // coordinates from the message and set the z coordinate to 0
-    t.transform.translation.x = msg->x;
-    t.transform.translation.y = msg->y;
+    t.transform.translation.x = msg.x;
+    t.transform.translation.y = msg.y;
     t.transform.translation.z = 0.0;
 
     // For the same reason, turtle can only rotate around one axis
     // and this why we set rotation in x and y to 0 and obtain
     // rotation in z axis from the message
     tf2::Quaternion q;
-    q.setRPY(0, 0, msg->theta);
+    q.setRPY(0, 0, msg.theta);
     t.transform.rotation.x = q.x();
     t.transform.rotation.y = q.y();
     t.transform.rotation.z = q.z();

diff --git a/source/Tutorials/Writing-A-Simple-Cpp-Publisher-And-Subscriber.rst b/source/Tutorials/Writing-A-Simple-Cpp-Publisher-And-Subscriber.rst
@@ -356,9 +356,13 @@ Open the ``subscriber_member_function.cpp`` with your text editor.
         }
 
       private:
+<<<<<<< HEAD
         void topic_callback(const std_msgs::msg::String::SharedPtr msg) const
+=======
+        void topic_callback(const std_msgs::msg::String & msg) const
+>>>>>>> e4cd3cb (Use `const&` signature for read-only sub callbacks (#2297))
         {
-          RCLCPP_INFO(this->get_logger(), "I heard: '%s'", msg->data.c_str());
+          RCLCPP_INFO(this->get_logger(), "I heard: '%s'", msg.data.c_str());
         }
         rclcpp::Subscription<std_msgs::msg::String>::SharedPtr subscription_;
     };
@@ -398,9 +402,13 @@ The only field declaration in this class is the subscription.
 .. code-block:: C++
 
     private:
+<<<<<<< HEAD
       void topic_callback(const std_msgs::msg::String::SharedPtr msg) const
+=======
+      void topic_callback(const std_msgs::msg::String & msg) const
+>>>>>>> e4cd3cb (Use `const&` signature for read-only sub callbacks (#2297))
       {
-        RCLCPP_INFO(this->get_logger(), "I heard: '%s'", msg->data.c_str());
+        RCLCPP_INFO(this->get_logger(), "I heard: '%s'", msg.data.c_str());
       }
       rclcpp::Subscription<std_msgs::msg::String>::SharedPtr subscription_;