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User Data Passing
Description: This tutorial gives an example of two states passing user data to each other.Tutorial Level: BEGINNER
Next Tutorial: Nesting State Machines
All of the following examples can be run without modification. They can be found in the smach_tutorials package in the examples directory. The comments at the head of each file show roughly what the output from running the script should look like.
1 #!/usr/bin/env python
2
3 import roslib; roslib.load_manifest('smach_tutorials')
4 import rospy
5 import smach
6 import smach_ros
7
8 # define state Foo
9 class Foo(smach.State):
10 def __init__(self):
11 smach.State.__init__(self,
12 outcomes=['outcome1','outcome2'],
13 input_keys=['foo_counter_in'],
14 output_keys=['foo_counter_out'])
15
16 def execute(self, userdata):
17 rospy.loginfo('Executing state FOO')
18 if userdata.foo_counter_in < 3:
19 userdata.foo_counter_out = userdata.foo_counter_in + 1
20 return 'outcome1'
21 else:
22 return 'outcome2'
23
24
25 # define state Bar
26 class Bar(smach.State):
27 def __init__(self):
28 smach.State.__init__(self,
29 outcomes=['outcome1'],
30 input_keys=['bar_counter_in'])
31
32 def execute(self, userdata):
33 rospy.loginfo('Executing state BAR')
34 rospy.loginfo('Counter = %f'%userdata.bar_counter_in)
35 return 'outcome1'
36
37
38
39
40
41 def main():
42 rospy.init_node('smach_example_state_machine')
43
44 # Create a SMACH state machine
45 sm = smach.StateMachine(outcomes=['outcome4'])
46 sm.userdata.sm_counter = 0
47
48 # Open the container
49 with sm:
50 # Add states to the container
51 smach.StateMachine.add('FOO', Foo(),
52 transitions={'outcome1':'BAR',
53 'outcome2':'outcome4'},
54 remapping={'foo_counter_in':'sm_counter',
55 'foo_counter_out':'sm_counter'})
56 smach.StateMachine.add('BAR', Bar(),
57 transitions={'outcome1':'FOO'},
58 remapping={'bar_counter_in':'sm_counter'})
59
60
61 # Execute SMACH plan
62 outcome = sm.execute()
63
64
65 if __name__ == '__main__':
66 main()
