[src/nav_node.cpp] Standardization of topic name

The previous code syntax forced the launch file programmer to write
explicitly the name of each topic, even if those names will be fixed (eg
"action_topic", "nav_stop"...).
Moreover when you write "/" before the
name of the topic, the name is "absolute" and can't be affected by
namespaces.

I removed the parameters to choose the name of topics, if we want to do
that, we can use a "remap" as it is usually done.
I also changed the name of topics to allow the use of namespace

Signed-off-by: Thomas Bonnefille <thomas.bonnefille@outlook.com>

src/nav_node.cpp

@@ -23,21 +23,16 @@ Nav_node::Nav_node() : Node("nav_node"){
     // Get parameters
 
     this->declare_parameter("robot_id", 0);
-    this->declare_parameter("pic_action_topic", "/pic_action");
-    this->declare_parameter("result_topic", "/result");
-    this->declare_parameter("robot_data_topic", "/robot_data");
-    this->declare_parameter("position_goal_topic", "/position_goal");
-    this->declare_parameter("stop_topic", "/stop");
     this->declare_parameter("normal_radius", 0.15);
     this->declare_parameter("variation_obs", 0.10);
     this->declare_parameter("map_file", "blank.txt");    
 
     this->robot_number = this->get_parameter("robot_id").as_int();
-    std::string pic_action_topic = this->get_parameter("pic_action_topic").as_string();
-    std::string result_topic = this->get_parameter("result_topic").as_string();
-    std::string robot_data_topic = this->get_parameter("robot_data_topic").as_string();
-    std::string position_goal_topic = this->get_parameter("position_goal_topic").as_string();
-    std::string stop_topic = this->get_parameter("stop_topic").as_string();
+    std::string pic_action_topic = "pic_action";
+    std::string result_topic = "nav_result";
+    std::string robot_data_topic = "robot_data";
+    std::string position_goal_topic = "nav_goal";
+    std::string stop_topic = "nav_stop";
     this->normal_radius = this->get_parameter("normal_radius").as_double();
     this->variation_obs = this->get_parameter("variation_obs").as_double();
     this->map_file = this->get_parameter("map_file").as_string();