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SERVICE - /bug0_switch

Provided by:

bug0.py

Used by:

user_console.py

Semantic

Tihis service is used for activating, or deactivating, the bug0.py node.

When it is turned on, the request is immediately accepted. Note well:

if the flag only_once is True, the algorithm takes the target from the parameter server (parameters des_pos_x and des_pos_y) with no checking on the validity (the node user_console is supposed to perform these checkings).
otherwise, the robot ciclically asks for a random position, and then tries to reach it.

The turn-off request is always immediately performed: the robot stops in the actual position.

Service code

SRV file

See the message switch_service.srv.

Set-up (Python)

from final_assignment.srv import switch_service, switch_serviceRequest, switch_serviceResponse
 
## name of the service 'reach_random_pos_switch'
name_reach_random_pos_switch = "/reach_random_pos_switch"
 
## === CLIENT SIDE ===
 
## call-point of the service 'reach_random_pos_switch'
srv_reach_random_pos_switch = None
 
# service 'reach_random_pos_switch'
rospy.loginfo( " [%s] getting service %s ...", node_name, name_reach_random_pos_switch )
rospy.wait_for_service( name_reach_random_pos_switch )
srv_reach_random_pos_switch = rospy.ServiceProxy( name_reach_random_pos_switch, switch_service )
rospy.loginfo( " [%s] service %s ... OK", node_name, name_reach_random_pos_switch )

How to use the service (Python)

Both the requests cannot fail in relevant cases; field in_progress is no use.

Non-blocking call. res.success = False when the node is already active.

global name_bug0_switch, srv_bug0_switch
 
# Turn on, in only once mode
#    REMEMBER WELL: set a destination before calling the service!
rospy.set_param("des_pos_x", x)
rospy.set_param("des_pos_y", y)
res = srv_bug0_switch( True, only_once=True )
# res.success = False when the node is already active. 
 
# Turn on, random target mode
res = srv_bug0_switch( True, False )
# res.success = False when the node is already active. 
 
# Turn off the service
srv_bug0_switch( False, False )