param 是一个字典，存储一些变量

param_demo.cpp

#include
     
      int main(int argc, char **argv){        ros::init(argc, argv, "param_demo");        ros::NodeHandle nh;        int parameter1, parameter2, parameter3, parameter4, parameter5;        //Get Param的三种方法        //① ros::param::get()获取参数“param1”的value，写入到parameter1上        bool ifget1 = ros::param::get("param1", parameter1);        //② ros::NodeHandle::getParam()获取参数，与①作用相同        bool ifget2 = nh.getParam("param2",parameter2);        //③ ros::NodeHandle::param()类似于①和②        //但如果get不到指定的param，它可以给param指定一个默认值(如33333)        nh.param("param3", parameter3, 33333);        if(ifget1)                ROS_INFO("Get param1 = %d", parameter1);        else                ROS_WARN("Didn't retrieve param1");       if(ifget2)                ROS_INFO("Get param2 = %d", parameter2);        else                ROS_WARN("Didn't retrieve param2");        if(nh.hasParam("param3"))                ROS_INFO("Get param3 = %d", parameter3);        else                ROS_WARN("Didn't retrieve param3");    //Set Param的两种方法        //① ros::param::set()设置参数        parameter4 = 4;        ros::param::set("param4", parameter4);        //② ros::NodeHandle::setParam()设置参数        parameter5 = 5;        nh.setParam("param5",parameter5);        ROS_INFO("Param4 is set to be %d", parameter4);        ROS_INFO("Param5 is set to be %d", parameter5);        //Check Param的两种方法        //① ros::NodeHandle::hasParam()        bool ifparam5 = nh.hasParam("param5");        //② ros::param::has()        bool ifparam6 = ros::param::has("param6");        if(ifparam5)                ROS_INFO("Param5 exists");        else                ROS_INFO("Param5 doesn't exist");        if(ifparam6)                ROS_INFO("Param6 exists");        else                ROS_INFO("Param6 doesn't exist");        //Delete Param的两种方法        //① ros::NodeHandle::deleteParam()        bool ifdeleted5 = nh.deleteParam("param5");        //② ros::param::del()        bool ifdeleted6 = ros::param::del("param6");        if(ifdeleted5)                ROS_INFO("Param5 deleted");        else                ROS_INFO("Param5 not deleted");        if(ifdeleted6)                ROS_INFO("Param6 deleted");        else                ROS_INFO("Param6 not deleted");        ros::Rate rate(0.3);        while(ros::ok()){                int parameter = 0;                ROS_INFO("=============Loop==============");                //roscpp中尚未有ros::param::getallparams()之类的方法                if(ros::param::get("param1", parameter))                        ROS_INFO("parameter param1 = %d", parameter);                if(ros::param::get("param2", parameter))                        ROS_INFO("parameter param2 = %d", parameter);                if(ros::param::get("param3", parameter))                        ROS_INFO("parameter param3 = %d", parameter);                if(ros::param::get("param4", parameter))                        ROS_INFO("parameter param4 = %d", parameter);                if(ros::param::get("param5", parameter))                        ROS_INFO("parameter param5 = %d", parameter);                if(ros::param::get("param6", parameter))                        ROS_INFO("parameter param6 = %d", parameter);                rate.sleep();        }}
     

 

param_demo_cpp.launch

         
          
          
          
          
          
      
                  param3: 3        param4: 4        param5: 5