Subscriber callback in class defined as shared_ptr

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Hi,

I have very weird problem. I'm trying to set callback function to one of my subscribers. The problem is that the object, in which the callback function is declared, is defined as std::shared_ptr. Let me give you an example. Assume we have 2 classes, class A and B.

Class A looks like this:

#include <ros/ros.h>

class A {
public:
    A(const ros::NodeHandle& nh) : nh_(nh), subscriber_(nh_.subscribe("topic", 10, &B::callback, b_.get())){
        b_ = std::make_shared<B>(nh_);    
    }

private:
    ros::NodeHandle nh_;
    ros::Subscriber subscriber_;    

    std::shared_ptr<B> b_;
};

And class B looks like this:

#include <ros/ros.h>
#include <geometry_msgs/PoseStamped.h>

class B {
public:
    B(const ros::NodeHandle& nh) : nh_(nh) {}

    callback(const geometry_msgs::PoseStampedConstPtr& pose){
        value_ = 1.0;
    }
private:
   double value_{0.0};
};

And this obviously doesn't work for some reason. The strange thing is that I can only ROS_INFO the data coming to my topic in callback function, but not modify any member variables in class B. I think it has to do something with callback function looking at "wrong place". Normally I can modify member variables without problem.

Is there some solution to this? Is it even possible to point callback to function in class defined as std::shared_ptr?

Thank you for any advice.