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First, am I right in assuming input_keys and output_keys are the preferred method of propagating information throughout a SMACH State Machine? From what I can see, this requires a good deal of bookeeping, but if there's no other way, then that's that.

I cannot get userdata passing between a State Machine and a Sub-Container. Here's what I would expect to work.

class QuickTestMain( smach.State ):
    def __init__( self, name ):
        smach.State.__init__( self, outcomes = ['succeeded','aborted','preempted'] )
        self.count = 0
        self.name = name

    def execute( self, userdata ):
        r = rospy.Rate( 1 )
        for i in xrange( 5 ):
            self.count += 1
            rospy.logout( '%s at count %3.2f' % (self.name, self.count))
        return 'succeeded'
class PrintStr(smach.State):
    def __init__(self, ins = 'Hello'):
        smach.State.__init__(self, outcomes=['succeeded', 'aborted', 'preempted'],
        self.ins = ins
    def execute(self, userdata):
        rospy.logout( 'Received input data: %s' % userdata.in_key )  
        return 'succeeded'
def sms():
    smc = smach.StateMachine( outcomes=['succeeded', 'aborted', 'preempted'],
    print smc.userdata.outtie # Fails
    with smc:
        smach.StateMachine.add('MAIN2', QuickTestMain('main2'),transitions={'succeeded':'succeeded'})
    return smc
if __name__ == '__main__':
    rospy.init_node( 'tmp_test')
    sm = smach.StateMachine(outcomes=['succeeded','aborted','preempted'],output_keys=['five'])
    print sm.userdata.five
    with sm:
        smach.StateMachine.add( 'PS1', PrintStr(), transitions={'succeeded':'SMS'},remapping={'in_key':'five'})
        smach.StateMachine.add( 'SMS', sms(), transitions={'succeeded':'succeeded'},remapping={'outtie':'five'})
    sis = IntrospectionServer( 'sm_test', sm, '/SM_TEST' )
    rospy.sleep( 5 )

I am attempting to pass userdata from a State Machine to a sub-SM with the remapping command, but apparently this doesn't work for Sub-SM ?

Is there anywhere in the docs I could get more info on this? Thanks

Originally posted by phil0stine on ROS Answers with karma: 682 on 2012-03-21

Post score: 2

Original comments

Comment by Mehdi. on 2014-06-30:
I don't remember seeing a declaration of a state as a function in the tutorials. Check the tutorial for nested states, it shows how to correctly declare a state as a substatemachine.


1 Answer 1


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Your sms() function is being called when you create the SMS state, not when the state is executed, so that is definitely going to fail.

W.r.t. userdata remapping, that maps userdata keys to other userdata keys, it does not "set" the value of a userdata key.

Originally posted by jbohren with karma: 5809 on 2014-07-03

This answer was ACCEPTED on the original site

Post score: 0


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