Example of simple state machine

README.md

@@ -5,3 +5,73 @@ SMACH is a task-level python execution framework for rapidly composing complex
 robot behaviors.
 
 ![travis](https://travis-ci.org/jbohren/executive_smach.svg?branch=master)
+
+# Example 
+
+```python
+import smach
+import rclpy
+from rclpy.node import Node
+
+# define state Foo
+class Foo(smach.State):
+    def __init__(self):
+        smach.State.__init__(self, outcomes=['outcome1','outcome2'])
+        self.counter = 0
+
+    def execute(self, userdata):
+        rclpy.logging.get_logger("foo").info('Executing state FOO')
+        if self.counter < 3:
+            self.counter += 1
+            return 'outcome1'
+        else:
+            return 'outcome2'
+
+
+# define state Bar
+class Bar(smach.State):
+    def __init__(self):
+        smach.State.__init__(self, outcomes=['outcome2'])
+
+    def execute(self, userdata):
+        rclpy.logging.get_logger("bar").info('Executing state BAR')
+        return 'outcome2'
+
+
+
+class SmachExampleStateMachine(Node):
+
+    def __init__(self):
+        super().__init__('smach_example_state_machine')
+
+        # Create a SMACH state machine
+        sm = smach.StateMachine(outcomes=['outcome4', 'outcome5'])
+
+        # Open the container
+        with sm:
+            # Add states to the container
+            smach.StateMachine.add('FOO', Foo(), 
+                                transitions={'outcome1':'BAR', 
+                                                'outcome2':'outcome4'})
+            smach.StateMachine.add('BAR', Bar(), 
+                                transitions={'outcome2':'FOO'})
+
+        # Execute SMACH plan
+        outcome = sm.execute()
+
+
+# main
+def main(args=None):
+    rclpy.init(args=args)
+
+    smach_example_state_machine = SmachExampleStateMachine()
+
+    rclpy.spin(smach_example_state_machine)
+
+    smach_example_state_machine.destroy_node()
+    rclpy.shutdown()
+
+
+if __name__ == '__main__':
+    main()
+```