使用ROS1遇到的问题

1，今天用rospy.Timer(Duaration, self.timer_callback)时一直报错：

        _callback takes 1 positional argument but 2 were given

回调函数是这样的：

callback(self):

        ****

        网上查了很多资料，都说类中的函数需要加self，就能解决这个问题，但我明明加了，google了一下：

加了event,完美解决~

2， 用launch文件launch节点后，发现print语句打印不到界面了

解决办法：<node pkg="**" type="**" name="**"  output="screen" />， 加上output

3，同一个ros节点同时订阅和发布，并在订阅的回调函数中发布另一个话题，这里的答案：

#include <ros/ros.h>

class SubscribeAndPublish
{
public:
  SubscribeAndPublish()
  {
    //Topic you want to publish
    pub_ = n_.advertise<PUBLISHED_MESSAGE_TYPE>("/published_topic", 1);

    //Topic you want to subscribe
    sub_ = n_.subscribe("/subscribed_topic", 1, &SubscribeAndPublish::callback, this);
  }

  void callback(const SUBSCRIBED_MESSAGE_TYPE& input)
  {
    PUBLISHED_MESSAGE_TYPE output;
    //.... do something with the input and generate the output...
    pub_.publish(output);
  }

private:
  ros::NodeHandle n_; 
  ros::Publisher pub_;
  ros::Subscriber sub_;

};//End of class SubscribeAndPublish

int main(int argc, char **argv)
{
  //Initiate ROS
  ros::init(argc, argv, "subscribe_and_publish");

  //Create an object of class SubscribeAndPublish that will take care of everything
  SubscribeAndPublish SAPObject;

  ros::spin();

  return 0;
}

持续更新中……