SMACH专题（三）----几种State类型

　　状态机提供了若干种状态，包括了Generic State，CBState，SimpleActionState (ROS)，ServiceState (ROS)，MonitorState (ROS)。下面分别介绍它们的用法和例子。

一、CBState回调状态

　　将一个函数封装成状态，这种状态成为回调状态。这种函数非类中的函数，而是一般的函数。下面是一个例子：

#!/usr/bin/env python
# license removed for brevity

import rospy
from std_msgs.msg import String
import math
import random
from smach import CBState, StateMachine
from smach_ros import IntrospectionServer
import smach

@smach.cb_interface(
                output_keys=['xyz'],
                outcomes=['outcome1','outcome2'])
def fun_cb(ud,x0, x, y, z):
    '''
    callback function, which is called in CBState way, it seems to be used by
    function, but the class'funtion
    '''
    #x0 is the value of  cb_args=[10], equal to 10
    dist = math.sqrt(x0*x0+x*x+y*y+z*z+100*random.random())
    ud.xyz = dist
    if dist > 10:
        return 'outcome1'
    else:
        return 'outcome2'
        
class Test_CbState():
    def __init__(self):
        rospy.init_node('smach_example_callback_state')
        self.sample_name = "cbstate"  
    
    def test(self):
        '''
        test Callback State Machine
        '''
        self.sm = StateMachine(outcomes = ['outcome3'])
        with self.sm:
            StateMachine.add('Test_CB',CBState(fun_cb,
                                               cb_args=[10],
                                               cb_kwargs={'x':1,'y':2,'z':3}),
                                               {'outcome1':'outcome3','outcome2':'Test_CB'})
        sis = IntrospectionServer('test_cb_state', self.sm, '/SM_ROOT')
        sis.start()
        
        self.sm.execute('Test_CB')
        
        rospy.spin()
        sis.stop()
        
if __name__ == '__main__':
    '''
    main funtion
    '''
    test_sm_cbstate = Test_CbState()
    test_sm_cbstate.test()
            

　　状态图，如下图所示：

　　参考资料：

　　　　[1]. CBState