calculation_state.py

Go to the documentation of this file.

#!/usr/bin/env python

import rospy
from flexbe_core import EventState, Logger

'''
Created on 29.08.2013

@author: Philipp Schillinger
'''

class CalculationState(EventState):
        '''
        Implements a state that can perform a calculation based on userdata.
        calculation is a function which takes exactly one parameter, input_value from userdata,
        and its return value is stored in output_value after leaving the state.
        
        -- calculation  function        The function that performs the desired calculation.
                                                                It could be a private function (self.foo) manually defined in a behavior's source code
                                                                or a lambda function (e.g., lambda x: x^2, where x will be the input_value).

        ># input_value  object          Input to the calculation function.

        #> output_value object          The result of the calculation.

        <= done                                         Indicates completion of the calculation.

        '''


        def __init__(self, calculation):
                '''
                Constructor
                '''
                super(CalculationState, self).__init__(outcomes=['done'],
                                                                                           input_keys=['input_value'],
                                                                                           output_keys=['output_value'])
                
                self._calculation = calculation
                self._calculation_result = None
                
                
        def execute(self, userdata):
                '''Execute this state'''

                userdata.output_value = self._calculation_result

                # nothing to check
                return 'done'


        def on_enter(self, userdata):
                
                if self._calculation is not None:
                        try:
                                self._calculation_result = self._calculation(userdata.input_value)
                        except Exception as e:
                                Logger.logwarn('Failed to execute calculation function!\n%s' % str(e))
                else:
                        Logger.logwarn('Passed no calculation!')