Boost Signals2 Connection Management

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C++

Boost

I have an application that is relying heavily on boost signals2. One issue that I want to address is that I do not want objects to be able to register a member function to a signal twice. Is there a mechanism to enforce that?

Looking at the tutorial, I don't really see this kind of enforcement documented.

http://www.boost.org/doc/libs/1_40_0/doc/html/signals2/tutorial.html

What I want is something like:

class HelloWorld
{
  public:
    HelloWorld()
    {
       this->_signal.connect(boost::bind(&HelloWorld::Hello, this)); // Connects
       this->_signal.connect(boost::bind(&HelloWorld::Hello, this)); // Desired: Does NOT Connect again.
       this->_signal.connect(boost::bind(&HelloWorld::World, this)); // Connects
       this->_signal.connect(boost::bind(&HelloWorld::World, this)); // Desired: Does NOT Connect again.
    }

    void operator()() const
    {
       this->_signal();
    }

    void Hello()
    {
      std::cout << "Hello ";
    }

    void World()
    {
      std::cout << "World!";
    }

  private:
    boost::signals2::signal<void> _signal;
};

// Desired Output: "Hello World!"</void>