Problems using Class Methods as Callbacks.

edit

Hi All, I have a weird issue that I am facing while using class methods as callbacks. I am going to try and summarize the issue here.

class A{
protected:
   int alpha;
} 
class B:public A{ 
 public:
   B(){ alpha = 1; }
   void some_func(){ alpha = 2; }
   void odom_callback(const nav_msgs::Odometry::ConstPtr& msg){ std::cout<<alpha;}
}
int main(){
B * var = new B;
B->some_ func();
ros::spin();
}

Now, when the odom callback is called, I would expect it to print 2 for the value of alpha. However, in the callback it keeps printing 1. I know for sure that some_func() has been called. However I do not know why in the callback it uses the first initialized value. Of course my real code is more complex, though I tried to illustrate the fault in this example. Please let me know what you think might be going wrong. Thanks! Ammar