The Code

Since we have already created a cfg file in the last tutorial we'll dive right in to the code. Go back to our dynamic_tutorials package, create a new directory called nodes, and another directory called src. In the nodes directory create a file called server.py. Drop the following code into server.py:

   1 #!/usr/bin/env python
   2 
   3 PACKAGE = 'dynamic_tutorials'
   4 import roslib;roslib.load_manifest(PACKAGE)
   5 import rospy
   6 
   7 from dynamic_reconfigure.server import Server
   8 from dynamic_tutorials.cfg import TutorialsConfig
   9 
  10 def callback(config, level):
  11     rospy.loginfo("""Reconfigure Request: {int_param}, {double_param},\ 
  12           {str_param}, {bool_param}, {size}""".format(**config))
  13     return config
  14 
  15 if __name__ == "__main__":
  16     rospy.init_node("dynamic_tutorials", anonymous = True)
  17 
  18     srv = Server(TutorialsConfig, callback)
  19     rospy.spin()

The Breakdown

Let's take a closer look at server.py:

   1 #!/usr/bin/env python
   2 
   3 PACKAGE = 'dynamic_tutorials'
   4 import roslib;roslib.load_manifest(PACKAGE)
   5 import rospy
   6 
   7 from dynamic_reconfigure.server import Server
   8 from dynamic_tutorials.cfg import TutorialsConfig

These first few lines are pretty simply we just set up ROS and import dynamic_reconfigure as well as our config type.

   1 def callback(config, level):
   2     rospy.loginfo("""Reconfiugre Request: {int_param}, {double_param},\ 
   3           {str_param}, {bool_param}, {size}""".format(**config))
   4     return config

Here we define a callback to be called when the configuration is updated, for the purposes of this tutorial we will simply print out the updated configuration.

   1 if __name__ == "__main__":
   2     rospy.init_node("dynamic_tutorials", anonymous = True)
   3 
   4     srv = Server(TutorialsConfig, callback)
   5     rospy.spin()

Lastly we initialize our node, construct a server, passing it our config type and our callback function, and spin the node.

Run It!

First we need to make the node executable:

chmod +x nodes/server.py

Now rosrun the node and the launch the reconfigure_gui using:

rosrun dynamic_reconfigure reconfigure_gui

You should see a window that looks something like this pop up.

And you're done! You've just built your first dynamically reconfigure-able node.