flexible_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 FlexibleCalculationState(EventState):
        '''
        Implements a state that can perform a calculation based on multiple userdata inputs provided as a list to the calculation function.
                
        -- 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[0]^2 + x[1]^2).
        -- input_keys   string[]    List of available input keys.

        ># input_keys   object[]    Input(s) to the calculation function as a list of userdata.
                                                                The individual inputs can be accessed as list elements (see lambda expression example).

        #> output_value object      The result of the calculation.

        <= done                     Indicates completion of the calculation.

        '''


        def __init__(self, calculation, input_keys):
                '''Constructor'''
                super(FlexibleCalculationState, self).__init__(outcomes=['done'],
                                                                                           input_keys=input_keys,
                                                                                           output_keys=['output_value'])
                
                self._calculation = calculation
                self._calculation_result = None
                self._input_keys = input_keys
                
                
        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(map(lambda key: userdata[key], self._input_keys))
                        except Exception as e:
                                Logger.logwarn('Failed to execute calculation function!\n%s' % str(e))
                else:
                        Logger.logwarn('Passed no calculation!')