实操 | std_msgs/Empty and std_srv_msgs/Empty

It is interesting and aslo necessary to disscuss about the two types in ROS, std_msgs/Empty and std_srv_msgs/Empty.

The two message type are indicating there are nothing to transmit but a trigger signal.

In a Publisher / Subscriber use case, std_msgs/Empty could be useful when we only want to trigger an event.

For example,

in C++:

#include <std_msgs/Empty.h>

int main(int argc, char **argv){

    init(argc, argv, "takeoff_fly");
    Nodehandle n;
    std_msg::Empty myMsg;
    Publisher takeOff=n.advertise<std_msgs::Empty>("/ardrone/takeoff",1);
    takeOff.publish(myMsg);
    spinOnce();

    return 0;
}

in Python:

from std_msgs.msg import Empty as EmptyMsg
takeOff = rospy.Publisher('/ardrone/takeoff', EmptyMsg, queue_size=1)

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