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Userdata change type

asked 2016-10-10 04:38:52 -0500

pv gravatar image

updated 2016-10-10 05:03:36 -0500

Hi,

I try to du a small smach tree and pass a class between the state with userdata, the code look like this

class Auto_move_info(object):
        __pallet_position = None
        __pallet_place_position = None

    def __init__(self, pallet_position=None, pallet_place_position=None):
        self.__pallet_position = pallet_position
        self.__pallet_place_position = pallet_place_position

    def set_pallet_position(self, pallet_position):
        self.__pallet_position = pallet_position

    def get_pallet_position(self):
        return self.__pallet_position

    def set_pallet_place_position(self, pallet_place_position):
        self.__pallet_place_position = pallet_place_position

    def get_pallet_place_position(self):
        return self.__pallet_place_position

class Get_pallet_position(smach.State):
    def __init__(self):
        smach.State.__init__(self, outcomes=['pallet_position_found'],
                            output_keys=['get_pallet_position_op'])
        self.move_pallet_A_to_X = Auto_move_info('A','X')

    def execute(self, userdata):
        time.sleep(2)   
        userdata.get_pallet_position_op = self.move_pallet_A_to_X
        print ("1")
        print(self.move_pallet_A_to_X)
        print ("2")
        rospy.loginfo('Get_pallet_position')
        return 'pallet_position_found'

class Calculate_pallet_position(smach.State):
    def __init__(self):
        smach.State.__init__(self, outcomes=['calculation_pallet_done'],
                            input_keys=['calculate_pallet_position_ip'],
                            output_keys=['calculate_pallet_position_op'])

    def execute(self, userdata):
        time.sleep(2)
        print ("3")
        print(userdata.calculate_pallet_position_ip)
        print ("4")
        rospy.loginfo('Executing state Calculate_pallet_position')
        return 'calculation_pallet_done'

The result the become:

[INFO] [WallTime: 1476091443.061490] State machine starting in initial state 'Get_pallet_position' with userdata: 
    []
1
<class_definition.Auto_move_info object at 0xb59ced2c>
2
[INFO] [WallTime: 1476091445.064946] Get_pallet_position
[INFO] [WallTime: 1476091445.065734] State machine transitioning 'Get_pallet_position':'pallet_position_found'-->'Calculate_pallet_position'
3
<smach.user_data.Const object at 0xb6158b4c>
4
[INFO] [WallTime: 1476091447.070927] Executing state Calculate_pallet_position

Why does the object move_pallet_A_to_X change from an Auto_move_info object to a Const?

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2 Answers

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answered 2016-10-12 02:09:24 -0500

pv gravatar image

It works, but I wounder if I can have any problem with that the input_key and the output_key has the same name? Should I do in some other way? Right now I have declared both like input and output but only one of them is remapping with another state.

class Calculate_pallet_position(smach.State):
    def __init__(self):
        smach.State.__init__(self, outcomes=['calculation_pallet_done'],
                            input_keys=['calculate_pallet_position_ip','calculate_pallet_position_op'],
                            output_keys=['calculate_pallet_position_ip','calculate_pallet_position_op'])


#-------------------------------------------------------------------------------    
    # Create the sub SMACH state machine 
        sm_go_to_pallet = smach.StateMachine(outcomes=['go_to_pallet_done'])

        # Open the container 
        with sm_go_to_pallet:

            # Add states to the container 
            smach.StateMachine.add('Get_pallet_position', Get_pallet_position(),
                                   transitions={'pallet_position_found':'Calculate_pallet_position'},
                                   remapping={'get_pallet_position_op':'calculate_pallet_position_ip'})

            smach.StateMachine.add('Calculate_pallet_position', Calculate_pallet_position(),
                                   transitions={'calculation_pallet_done':'Move_forklift_to_pallet'},
                                   remapping={'calculate_pallet_position_op':'move_forklift_to_pallet_ip'})
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Comments

It is completely fine to use a userdata key as input and output. If you need to use a custom class instantiation in userdata, this reflects the fact that calling methods on this object might have side effects.

Philipp Schillinger gravatar imagePhilipp Schillinger ( 2016-10-12 13:18:07 -0500 )edit

Thanks for the answers!

pv gravatar imagepv ( 2016-10-13 08:27:23 -0500 )edit
1

answered 2016-10-11 16:39:29 -0500

Not sure if this is the reason here, but could very well be the case: If a userdata key is only declared as input key, but not as output key, it is read-only. This could explain why it appears as Const object.

Could you try to declare it as output key as well in the second state?

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Asked: 2016-10-10 04:38:52 -0500

Seen: 142 times

Last updated: Oct 12 '16