ROS中的ConstPtr&

void chatterCallback(const std_msgs::String::ConstPtr& msg) 

     {ROS_INFO("I heard: [%s]", msg->data.c_str());}

 

When messages are automatically generated into C++ code, there are several typedefs defined. One of them is ::Ptr, which is typedef-ed to be a boost::shared_ptr, and another is ::ConstPtr which is boost::shared_ptr.

By passing a const pointer into the callback, we avoid doing a copy. While this might not make much difference for std_msgs::String, it can make a huge difference for sensor_msgs::PointCloud2.

 

https://answers.ros.org/question/212857/what-is-constptr/