flexible_check_condition_state.py

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#!/usr/bin/env python

import rospy
from flexbe_core import EventState, Logger

'''
Created on 08.11.2016

@author: Alberto Romay
'''

class FlexibleCheckConditionState(EventState):
        '''
        Implements a state that checks if the given condition is true based on multiple userdata inputs provided as a list to the calculation function
                                                                and returns the corresponding outcome.
        This state can be used if the further control flow of the behavior depends on a simple condition.

        -- predicate  function      The condition whose truth value will be evaluated.
                                                                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).

        <= true                                         Returned if the condition evaluates to True
        <= false                                        Returned if the condition evaluates to False

        '''


        def __init__(self, predicate, input_keys):
                '''Constructor'''
                super(FlexibleCheckConditionState, self).__init__(outcomes=['true', 'false'],
                                                                                           input_keys=input_keys)

                self._input_keys = input_keys
                self._predicate  = predicate
                self._outcome    = 'false'


        def execute(self, userdata):
                '''Execute this state'''

                return self._outcome


        def on_enter(self, userdata):

                if self._predicate is not None:
                        try:
                                self._outcome = "true" if self._predicate(map(lambda key: userdata[key], self._input_keys)) else 'false'
                        except Exception as e:
                                Logger.logwarn('Failed to execute condition function!\n%s' % str(e))
                else:
                        Logger.logwarn('Passed no predicate!')