ROS2 Message filters in a class, initializing message_filters::Subscriber object

asked 2020-08-15 19:17:57 -0600

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updated 2020-08-16 11:28:50 -0600

I am trying to sync two message streams of 2 image topics. So I am using message filters. I was using a class to do all this, however, the member initialisation doesn't work for me for message_filters::Subscriber. This is my code-

class MultiSubscriber : public rclcpp::Node
{
  public:

      message_filters::Subscriber<sensor_msgs::msg::Image> image_sub_;
      message_filters::Subscriber<sensor_msgs::msg::Image> disparity_sub_;

    MultiSubscriber(const std::string& name)
    : Node(name), 
      image_sub_(message_filters::Subscriber<sensor_msgs::msg::Image>(this, "image_color_topic")),
      disparity_sub_(message_filters::Subscriber<sensor_msgs::msg::Image>(this, "image_disparity_topic"))
    {

      typedef message_filters::sync_policies::ApproximateTime<sensor_msgs::msg::Image, sensor_msgs::msg::Image> approximate_policy;
      message_filters::Synchronizer<approximate_policy>syncApproximate(approximate_policy(10), image_sub_, disparity_sub_);

      syncApproximate.registerCallback(&MultSubscriber::disparityCb,this);


    }
    private:
    void disparityCb(const sensor_msgs::msg::Image::SharedPtr disparity_msg, const sensor_msgs::msg::Image::SharedPtr color_msg){
   //dosomething
                }
};

Because of these 2 lines-

  image_sub_(message_filters::Subscriber<sensor_msgs::msg::Image>(this, "image_color_topic")),
  disparity_sub_(message_filters::Subscriber<sensor_msgs::msg::Image>(this, "image_disparity_topic"))

I get this error-

/home/hsharma/Documents/internship/ws/ros2_ws/src/stereo_ground_surface/obstacle_detection/src/multisense_subscriber.cpp: In constructor ‘MultiSenseSubscriber::MultiSenseSubscriber(const string&)’:
/home/hsharma/Documents/internship/ws/ros2_ws/src/stereo_ground_surface/obstacle_detection/src/multisense_subscriber.cpp:68:120: error: use of deleted function ‘message_filters::Subscriber<sensor_msgs::msg::Image_<std::allocator<void> > >::Subscriber(const message_filters::Subscriber<sensor_msgs::msg::Image_<std::allocator<void> > >&)’
     : Node(name), image_sub_(message_filters::Subscriber<sensor_msgs::msg::Image>(this, "/multisense/left/image_color"))
                                                                                                                        ^
In file included from /home/hsharma/Documents/internship/ws/ros2_ws/src/stereo_ground_surface/obstacle_detection/src/multisense_subscriber.cpp:10:0:
/opt/ros/eloquent/include/message_filters/subscriber.h:102:7: note: ‘message_filters::Subscriber<sensor_msgs::msg::Image_<std::allocator<void> > >::Subscriber(const message_filters::Subscriber<sensor_msgs::msg::Image_<std::allocator<void> > >&)’ is implicitly deleted because the default definition would be ill-formed:
 class Subscriber : public SubscriberBase, public SimpleFilter<M>
       ^~~~~~~~~~
/opt/ros/eloquent/include/message_filters/subscriber.h:102:7: error: use of deleted function ‘message_filters::SimpleFilter<sensor_msgs::msg::Image_<std::allocator<void> > >::SimpleFilter(const message_filters::SimpleFilter<sensor_msgs::msg::Image_<std::allocator<void> > >&)’
In file included from /opt/ros/eloquent/include/message_filters/subscriber.h:41:0,
                 from /home/hsharma/Documents/internship/ws/ros2_ws/src/stereo_ground_surface/obstacle_detection/src/multisense_subscriber.cpp:10:
/opt/ros/eloquent/include/message_filters/simple_filter.h:57:7: note: ‘message_filters::SimpleFilter<sensor_msgs::msg::Image_<std::allocator<void> > >::SimpleFilter(const message_filters::SimpleFilter<sensor_msgs::msg::Image_<std::allocator<void> > >&)’ is implicitly deleted because the default definition would be ill-formed:
 class SimpleFilter : public noncopyable
       ^~~~~~~~~~~~
/opt/ros/eloquent/include/message_filters/simple_filter.h:57:7: error: use of deleted function ‘message_filters::noncopyable::noncopyable(const message_filters::noncopyable&)’
In file included from /opt/ros/eloquent/include/message_filters/subscriber.h:40:0,
                 from /home/hsharma/Documents/internship/ws/ros2_ws/src/stereo_ground_surface/obstacle_detection/src/multisense_subscriber.cpp:10:
/opt/ros/eloquent/include/message_filters/connection.h:51:3: note: declared here
   noncopyable( const noncopyable& ) = delete;
   ^~~~~~~~~~~
In file included from /opt/ros/eloquent/include/message_filters/subscriber.h:41:0,
                 from /home/hsharma/Documents/internship/ws/ros2_ws/src/stereo_ground_surface/obstacle_detection/src/multisense_subscriber.cpp:10:
/opt/ros/eloquent/include/message_filters/simple_filter.h:57:7: error: use of deleted function ‘message_filters::Signal1<sensor_msgs::msg::Image_<std::allocator<void> > >::Signal1(const message_filters::Signal1<sensor_msgs::msg::Image_<std::allocator<void> > >&)’
 class SimpleFilter : public noncopyable
       ^~~~~~~~~~~~
In file included from /opt/ros/eloquent/include/message_filters/simple_filter.h:43:0,
                 from /opt ...

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Comments

Do you need to use the initializer list for construction? Can you try to initialize through the constructor as below?

Note the default Quality of Service profile would be used in the example below.

image_sub_.subscribe(this, "image_color_topic");
disparity_sub_.subscribe(this, "image_disparity_topic");

surfertas ( 2020-08-16 08:07:25 -0600 )edit

Thanks your method works. Would be good if I can pass qos variable too. Side note, It doesn't work with this too, I get the same error-

 MultiSubscriber(const std::string& name)
    : Node(name), 
    {
     image_sub_=message_filters::Subscriber<sensor_msgs::msg::Image>(this, "/multi/left/image_color",qos);
     disparity_sub_= message_filters::Subscriber<sensor_msgs::msg::Image>(this, "/multi/left/disparity");
      typedef message_filters::sync_policies::ApproximateTime<sensor_msgs::msg::Image, sensor_msgs::msg::Image> approximate_policy;
      message_filters::Synchronizer<approximate_policy>syncApproximate(approximate_policy(10), image_sub_, disparity_sub_);

      // register the exact time callback
      syncApproximate.registerCallback(&MultiSubscriber::disparityCb,this);

    }

Probably the question could be interpreted as how do I assign the subscription topic and qos to the message_filters::subscriber object ?

Harsh2308 ( 2020-08-16 11:27:27 -0600 )edit

My guess is copying a message_filters::Subscriber is not allowed and what I am doing above is copying a newly created message_filters::Subscriber object's values to another object I previously created.

Harsh2308 ( 2020-08-16 11:30:48 -0600 )edit

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