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通信过程

1.Talker 设置参数
Talker 通过 RPC 向参数服务器发送参数(包括参数名与参数值)，ROS Master 将参数保存到参数列表中。

2.Listener 获取参数
Listener 通过 RPC 向参数服务器发送参数查找请求，请求中包含要查找的参数名。

3.ROS Master 向 Listener 发送参数值
ROS Master 根据步骤2请求提供的参数名查找参数值，并将查询结果通过 RPC 发送给 Listener。

参数可使用数据类型:

32-bit integersbooleansstringsdoublesiso8601 dateslistsbase64-encoded binary data

新建参数服务器包

catkin_create_pkg paramservice std_msgs rospy roscpp

编写测试文件

#include "ros/ros.h"
#include <vector>
#include <map>
int main(int argc, char *argv[])
{//使得中文可以生效setlocale(LC_ALL,"");ros::init(argc,argv,"set_update_param");std::vector<std::string> stus;stus.push_back("这是元素1");stus.push_back("这是元素2");std::map<std::string,std::string> friends;friends["key"] = "value";ros::param::set("param_int",20);ros::param::set("param_double",3.14);ros::param::set("param_string","Hello Param");ros::param::set("param_bool",false);ros::param::set("param_vector",stus);ros::param::set("param_map",friends);//修改演示(相同的键，不同的值)ros::param::set("param_int",20000);// getParam 函数int param_int_value;double param_double_value;bool param_bool_value;std::string param_string_value;std::vector<std::string> param_stus;std::map<std::string, std::string> param_friends;ros::param::get("param_int",param_int_value);ros::param::get("param_double",param_double_value);ros::param::get("param_bool",param_bool_value);ros::param::get("param_string",param_string_value);ros::param::get("param_vector",param_stus);ros::param::get("param_map",param_friends);ROS_INFO("getParam获取的结果:%d,%.2f,%s,%d",param_int_value,param_double_value,param_string_value.c_str(),param_bool_value);for (auto &&stu : param_stus){ROS_INFO("stus 元素:%s",stu.c_str());        }for (auto &&f : param_friends){ROS_INFO("map 元素:%s = %s",f.first.c_str(), f.second.c_str());}//  首次调用getCached，这里会订阅参数值，通过缓存获取数据，当数据变化时，将通知节点自动更新ros::param::getCached("param_int",param_int_value);ROS_INFO("通过缓存获取数据:%d",param_int_value);//输出所有的变量名std::vector<std::string> param_names2;ros::param::getParamNames(param_names2);for (auto &&name : param_names2){ROS_INFO("名称解析name = %s",name.c_str());        }ROS_INFO("----------------------------");ROS_INFO("存在 param_int 吗? %d",ros::param::has("param_int"));ROS_INFO("存在 param_intttt 吗? %d",ros::param::has("param_intttt"));std::string key;ros::param::search("param_int",key);ROS_INFO("搜索键:%s",key.c_str());//删除相关的参数bool r2 = ros::param::del("param_int");ROS_INFO("param 删除结果:%d",r2);return 0;}

修改cmakelist:

add_executable(${PROJECT_NAME}_node src/paramservice.cpp)
target_link_libraries(${PROJECT_NAME}_node${catkin_LIBRARIES}
)

搭配launch文件

<launch><node name="myservice" pkg="service" type="service_node" output="screen"/>
</launch>

启动测试及结果

roslaunch paramservice start.launch

[ INFO] [1723529188.541091451]: getParam获取的结果:20000,3.14,Hello Param,0
[ INFO] [1723529188.541155371]: stus 元素:这是元素1
[ INFO] [1723529188.541178505]: stus 元素:这是元素2
[ INFO] [1723529188.541192963]: map 元素:key = value
[ INFO] [1723529188.542024132]: 通过缓存获取数据:20000
[ INFO] [1723529188.542419343]: 名称解析name = /run_id
[ INFO] [1723529188.542439561]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__34167
[ INFO] [1723529188.542458326]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__41769
[ INFO] [1723529188.542474146]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__45931
[ INFO] [1723529188.542489685]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__45545
[ INFO] [1723529188.542505965]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__44877
[ INFO] [1723529188.542524019]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__42835
[ INFO] [1723529188.542541943]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__46297
[ INFO] [1723529188.542559517]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__41351
[ INFO] [1723529188.542576629]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__43881
[ INFO] [1723529188.542594843]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__43899
[ INFO] [1723529188.542612596]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__34115
[ INFO] [1723529188.542630069]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__39145
[ INFO] [1723529188.542647101]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__43455
[ INFO] [1723529188.542664524]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__33051
[ INFO] [1723529188.542682467]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__35169
[ INFO] [1723529188.542700181]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__46493
[ INFO] [1723529188.542718104]: 名称解析name = /roslaunch/uris/host_yisu_64fc150f8284e__39659
[ INFO] [1723529188.542735557]: 名称解析name = /rosversion
[ INFO] [1723529188.542753210]: 名称解析name = /rosdistro
[ INFO] [1723529188.542771264]: 名称解析name = /param_double
[ INFO] [1723529188.542789378]: 名称解析name = /param_string
[ INFO] [1723529188.542806159]: 名称解析name = /param_bool
[ INFO] [1723529188.542823351]: 名称解析name = /param_vector
[ INFO] [1723529188.542840955]: 名称解析name = /param_map/key
[ INFO] [1723529188.542858317]: 名称解析name = /param_int
[ INFO] [1723529188.542878054]: ----------------------------
[ INFO] [1723529188.543220015]: 存在 param_int 吗? 1
[ INFO] [1723529188.543525068]: 存在 param_intttt 吗? 0
[ INFO] [1723529188.543831122]: 搜索键:/param_int
[ INFO] [1723529188.544247053]: param 删除结果:1