Where should I put MultiThreadedSpinner.spin() in my main function?

edit

HI I have a question about ros::MultiThreadedSpinner. I have several callback functions that should be handled at the same time so I am using Multi threads. The problem is that I need to call update function from my docking class continuously, like I did in the code below. In this case, is putting spinner.spin() above the while loop correct? I am not sure where I should place spinner.spin(), can someone tell me if I've done this in a right way and if the usage of multi thread like this is a common practice? Thank you in advance!

ros::init (argc, argv, "docking_node");
docking GGG;    
ros::MultiThreadedSpinner spinner(4);
ros::Rate spin_rate(10);


spinner.spin();
while(ros::ok){
    GGG.update();
    spin_rate.sleep();
}

return (0);