同じノード内で、トピックをsubscribeした後その内容に応じてトピックをpublishしたいという状況はよくあると思います。
ROS Wiki ではこの方法についてあまり触れていないので、ここにまとめておきます。
同じノードで行うためには、subscriberが呼び出すcallback関数の中でpublisherを使えるようにする必要があります。
そのため、以下のようにクラスを定義します。
#include "ros/ros.h"
#include "sensor_msgs/Image.h"
class SubPub
{
private:
ros::NodeHandle n_;
ros::Publisher pub_;
ros::Subscriber sub_;
public:
void callback(const sensor_msgs::Image &msg_sub);
SubPub()
{
sub_ = n_.subscribe("/topic_sub", 1000, &SubPub::callback, this);
pub_ = n_.advertise<sensor_msgs::Image>("/topic_pub", 1000);
}
};
void SubPub::callback(const sensor_msgs::Image &msg_sub)
{
sensor_msgs::Image msg_pub;
// 処理
pub_.publish(msg_pub);
}
int main(int argc, char *argv[])
{
ros::init(argc, argv, "node_subpub");
SubPub subpub;
ros::spin();
}/topic_sub というトピックをsubscribeし、/topic_pub というトピックをpublishするようにしています。
また、メッセージ型としては、sensor_msgs::Image をsubscribeし、同じ型をpublishするようにしています。
トピック名やメッセージ型は適宜変更してください。
上記コードのように、subscriberとpublisherをクラスのプライベートメンバ変数として持つことで、メンバ関数のcallbackがpublisherにアクセスできるようにしています。
実際に使うときには、上記main関数のように、クラスのインスタンスを1つ生成すればOKです。
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