[C++知识库]【ROS｜Bug】Cannot use ros::Time::now() before the first NodeHandle has been created 解决方法

报错输出

terminate called after throwing an instance of 'ros::TimeNotInitializedException'
  what():  Cannot use ros::Time::now() before the first NodeHandle has been created or ros::start() has been called.  If this is a standalone app or test that just uses ros::Time and does not communicate over ROS, you may also call ros::Time::init()
Aborted (core dumped)

原因及解决方法

参考链接：ROS 社区

除了在 ros::Time::now() 之前需要创建 ROS 节点，在 ros::Rate ， ros::ok() 和 ros::spinOnce() 之前都需要先创建 ROS 节点。
由于我是使用 C++ 类来实现消息的订阅和发布，所以需要使用初始化列表，在调用 ros::Rate
的构造函数之前，调用 ros::NodeHandle 的构造函数。

#include <ros/ros.h>

class Uav
{
public:
    Uav();
    ros::NodeHandle nh;

    //the setpoint publishing rate MUST be faster than 2Hz
    ros::Rate rate;  
};

Uav::Uav():nh(), rate(20.0)
{
}