services.py
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00032 
00033 from threading import Thread
00034 from rospy import ServiceProxy, resolve_name
00035 from rosservice import get_service_type
00036 from rosbridge_library.internal.ros_loader import get_service_class
00037 from rosbridge_library.internal.ros_loader import get_service_request_instance
00038 from rosbridge_library.internal.message_conversion import populate_instance
00039 from rosbridge_library.internal.message_conversion import extract_values
00040 
00041 
00042 class InvalidServiceException(Exception):
00043     def __init__(self, servicename):
00044         Exception.__init__(self, "Service %s does not exist" % servicename)
00045 
00046 
00047 class ServiceCaller(Thread):
00048 
00049     def __init__(self, service, args, success_callback, error_callback):
00050         """ Create a service caller for the specified service.  Use start()
00051         to start in a separate thread or run() to run in this thread.
00052 
00053         Keyword arguments:
00054         service          -- the name of the service to call
00055         args             -- arguments to pass to the service.  Can be an
00056         ordered list, or a dict of name-value pairs.  Anything else will be
00057         treated as though no arguments were provided (which is still valid for
00058         some kinds of service)
00059         success_callback -- a callback to call with the JSON result of the
00060         service call
00061         error_callback   -- a callback to call if an error occurs.  The
00062         callback will be passed the exception that caused the failure
00063 
00064          """
00065         Thread.__init__(self)
00066         self.daemon = True
00067         self.service = service
00068         self.args = args
00069         self.success = success_callback
00070         self.error = error_callback
00071 
00072     def run(self):
00073         try:
00074             # Call the service and pass the result to the success handler
00075             self.success(call_service(self.service, self.args))
00076         except Exception as e:
00077             # On error, just pass the exception to the error handler
00078             self.error(e)
00079 
00080 
00081 def args_to_service_request_instance(service, inst, args):
00082     """ Populate a service request instance with the provided args
00083 
00084     args can be a dictionary of values, or a list, or None
00085 
00086     Propagates any exceptions that may be raised. """
00087     msg = {}
00088     if isinstance(args, list):
00089         msg = dict(zip(inst.__slots__, args))
00090     elif isinstance(args, dict):
00091         msg = args
00092 
00093     # Populate the provided instance, propagating any exceptions
00094     populate_instance(msg, inst)
00095 
00096 
00097 def call_service(service, args=None):
00098     # Given the service name, fetch the type and class of the service,
00099     # and a request instance
00100 
00101     service = resolve_name(service)
00102 
00103     service_type = get_service_type(str(service))
00104     if service_type is None:
00105         raise InvalidServiceException(service)
00106     service_class = get_service_class(service_type)
00107     inst = get_service_request_instance(service_type)
00108 
00109     # Populate the instance with the provided args
00110     args_to_service_request_instance(service, inst, args)
00111 
00112     # Call the service
00113     proxy = ServiceProxy(service, service_class)
00114     response = proxy.call(inst)
00115 
00116     # Turn the response into JSON and pass to the callback
00117     json_response = extract_values(response)
00118 
00119     return json_response


rosbridge_library
Author(s): Jonathan Mace
autogenerated on Thu Aug 27 2015 14:50:35