4a: Services - example slides |

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Example: WordCount.srv

• WordCount.srv shows that it will take one input (string) and give one output (uint32)
• Notice some hairy tweaks of both CMakeLists.txt and package.xml
• Once done run catkin make ($ cm) to process and do the code generation
• You will immediately be able to see the service declared with $ rossrv show WordCount

Defining the logic

• It looks a lot like a node subscribing to a topic
• Big difference is that it has a ‘return’ statement
• In this example, it returns an integer equal to the number of words
• The money quote: return len(request.words.split())
• Notice the two ways of returning the result
• Everything else is plumbing

Implementing a Service

• Run the service with a standard rosrun command
• Remember our package is called samples
• Remember that you must have roscore running!
• rosrun samples service_server.py
• You can tell that it worked:
  1. It shows up in $ rosservice list
  2. It shows up in $ rosservice info word_count