古月居——ros_21_tutorials__代码更正2

#终端显示错误类型为：
/home/why/catkin_ws/src/learning_service/src/turtle_command_server.cpp:29:5: error: expected ‘;’ before ‘return’
return true;
^
learning_service/CMakeFiles/turtle_command_server.dir/build.make:62: recipe for target ‘learning_service/CMakeFiles/turtle_command_server.dir/src/turtle_command_server.cpp.o’ failed
make[2]: *** [learning_service/CMakeFiles/turtle_command_server.dir/src/turtle_command_server.cpp.o] Error 1
CMakeFiles/Makefile2:444: recipe for target ‘learning_service/CMakeFiles/turtle_command_server.dir/all’ failed
make[1]: *** [learning_service/CMakeFiles/turtle_command_server.dir/all] Error 2
Makefile:138: recipe for target ‘all’ failed
make: *** [all] Error 2
Invoking “make -j4 -l4” failed

错误出现在：工程ros_21_tutorials下功能包learning_service的src目录下turtle_command_server.cpp文件

更正后的代码如下

/***********************************************************************
Copyright 2020 GuYueHome (www.guyuehome.com).
***********************************************************************/

/**
 * 该例程将执行/turtle_command服务，服务数据类型std_srvs/Trigger
 */
 
#include <ros/ros.h>
#include <geometry_msgs/Twist.h>
#include <std_srvs/Trigger.h>

ros::Publisher turtle_vel_pub;
bool pubCommand = false;

// service回调函数，输入参数req，输出参数res
bool commandCallback(std_srvs::Trigger::Request  &req,
         	    std_srvs::Trigger::Response &res)
{
    
    
	pubCommand = !pubCommand;

    // 显示请求数据
    ROS_INFO("Publish turtle velocity command [%s]", pubCommand==true?"Yes":"No");

	// 设置反馈数据
	res.success = true;
	res.message = "Change turtle command state!";

    return true;
}

int main(int argc, char **argv)
{
    
    
    // ROS节点初始化
    ros::init(argc, argv, "turtle_command_server");

    // 创建节点句柄
    ros::NodeHandle n;

    // 创建一个名为/turtle_command的server，注册回调函数commandCallback
    ros::ServiceServer command_service = n.advertiseService("/turtle_command", commandCallback);

	// 创建一个Publisher，发布名为/turtle1/cmd_vel的topic，消息类型为geometry_msgs::Twist，队列长度10
	turtle_vel_pub = n.advertise<geometry_msgs::Twist>("/turtle1/cmd_vel", 10);

    // 循环等待回调函数
    ROS_INFO("Ready to receive turtle command.");

	// 设置循环的频率
	ros::Rate loop_rate(10);

	while(ros::ok())
	{
    
    
		// 查看一次回调函数队列
    	ros::spinOnce();
		
		// 如果标志为true，则发布速度指令
		if(pubCommand)
		{
    
    
			geometry_msgs::Twist vel_msg;
			vel_msg.linear.x = 0.5;
			vel_msg.angular.z = 0.2;
			turtle_vel_pub.publish(vel_msg);
		}

		//按照循环频率延时
	    loop_rate.sleep();
	}

    return 0;
}```