Boost Signals2 tracking - c++

Question

I am using Boost Signals2 in one of our project.In this I want automatic connection management,for this I am testing Boost Signals2 tracking but I am not getting slot invoked.
After I run following code , slots are not called .
Environment:
VS 2010,windows 7,boost 1.54
#include <stdio.h>
#include <iostream>
#include <string>
#include <boost/bind.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <boost/signals2/signal.hpp>
#include <boost/shared_ptr.hpp>
typedef boost::signals2::signal<void ()> signal_test;
using namespace boost;
class SubjectTest
{
public:
void Connect(const signal_test::slot_type &subscriber)
{
m_Signal.connect(subscriber);
std::cout << "No of connections : " << m_Signal.num_slots() << std::endl;
}
void Notify()
{
m_Signal();
}
private:
signal_test m_Signal;
};
class Listner
{
public:
Listner(){}
~Listner(){}
Listner(std::string name)
:m_name(name)
{
}
void GotSignal()
{
std::cout << m_name << std::endl;
}
void ConnectWithTracking(SubjectTest *s)
{
shared_ptr<Listner> l = new Listner();
s->Connect(signal_test::slot_type(&Listner::GotSignal,l.get()).track(l));
}
void ConnectNormal(SubjectTest *s)
{
s->Connect(bind(&Listner::GotSignal,this));
}
private:
std::string m_name;
shared_ptr<Listner> l;
};
void main()
{
Listner l2("First");
SubjectTest sub;
try
{
l2.ConnectWithTracking(&sub);
//l2.ConnectNormal(&sub);
sub.Notify();
{
Listner l3("Second");
l3.ConnectWithTracking(&sub);
//l3.ConnectNormal(&sub);
sub.Notify();
}
sub.Notify();
}
catch(std::exception ex)
{
std::cout << ex.what() << std::endl;
}
std::cout << "Finish" <<std::endl;
}
Updated :
*Working now*
#include <stdio.h>
#include <iostream>
#include <string>
#include <boost/bind.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <boost/signals2/signal.hpp>
#include <boost/shared_ptr.hpp>
typedef boost::signals2::signal<void ()> signal_test;
using namespace boost;
class SubjectTest
{
public:
void Connect(const signal_test::slot_type &subscriber)
{
m_Signal.connect(subscriber);
std::cout << "No of connections : " << m_Signal.num_slots() << std::endl;
}
void Notify()
{
m_Signal();
}
private:
signal_test m_Signal;
};
class Listner : public boost::enable_shared_from_this<Listner>
{
public:
Listner(){}
~Listner(){}
Listner(std::string name)
:m_name(name)
{
}
void GotSignal()
{
std::cout << m_name << std::endl;
}
void ConnectWithTracking(SubjectTest *s)
{
s->Connect(signal_test::slot_type(&Listner::GotSignal,shared_from_this().get()).track(shared_from_this()));
}
void ConnectNormal(SubjectTest *s)
{
s->Connect(bind(&Listner::GotSignal,this));
}
private:
std::string m_name;
};
void main()
{
shared_ptr<Listner> l2(new Listner("First"));
SubjectTest sub;
try
{
l2->ConnectWithTracking(&sub);
sub.Notify();
{
shared_ptr<Listner> l3(new Listner("Second"));
l3->ConnectWithTracking(&sub);
//l3.ConnectNormal(&sub);
sub.Notify();
}
sub.Notify();
}
catch(std::exception ex)
{
std::cout << ex.what() << std::endl;
}
std::cout << "Finish" <<std::endl;
}
Now this is complete example of Signal2 Automatic Connection Management

Answer 1

{
shared_ptr<Listner> l(new Listner());
s->Connect(signal_test::slot_type(&Listner::GotSignal,l.get()).track(l));
}
In the above lines l pointee gets destroyed at the closing } - meaning that the slot you just connected got expired.
The whole point of tracking is to pass to track() a shared_ptr (or weak_ptr), which is bound (or tightly related) to the slot itself. It doesn't make sense to pass a shared_ptr whose lifespan is unrelated to that of the slot itself.