ros::spin();的作用

ros::spin()是ROS中的一个函数，它的作用是让ROS节点不停地循环等待接收消息并处理。当ROS节点调用ros::spin()时，它会开始运行一个事件循环，不断地接收消息并调用相应的回调函数来处理消息。这个循环会一直运行，直到ROS节点被停止或者被关闭。因此，在使用ROS时，通常需要在节点的最后调用ros::spin()函数，以确保节点能够一直运行，等待接收消息并处理。

相关问题

ros::spinOnce() ros::spin()

In ROS, there are two commonly used functions for handling callbacks: ros::spinOnce() and ros::spin().

ros::spinOnce() allows ROS to process any pending callbacks once, but then returns control to the calling thread. This is useful when you have a loop that needs to keep running, but you need to periodically check for new data or events.

ros::spin(), on the other hand, is a blocking call that does not return control to the calling thread until the node is shut down. This is useful when you have a node that needs to run continuously and respond to events or data as they come in.

In general, you should use ros::spinOnce() if you have a loop that needs to keep running, and ros::spin() if you have a node that needs to run continuously. However, there are some cases where you may need to use both functions together, such as if you have multiple nodes running in the same process.

ros::Timer timer = nh.createTimer(ros::Duration(0), creat_callback); ros::spin()

这段代码创建了一个周期为0秒的ROS计时器，并指定当计时器超时时调用名为`creat_callback`的回调函数。接着，通过调用`ros::spin()`函数来使ROS节点进入自循环状态，等待来自ROS系统的事件（例如计时器超时事件、消息到达事件等）。在自循环状态下，ROS会不断地检查是否有事件发生，如果有则会调用相应的回调函数来处理事件。因为计时器的周期为0秒，所以它会立即超时并执行回调函数。而通过调用`ros::spin()`函数，ROS节点会一直等待事件的发生，直到节点被关闭。所以这段代码会在计时器超时后执行回调函数，并一直等待事件的发生，直到节点被关闭。