[boost] [signals] Replacing a connected slot

From: Jody Hagins (jody-boost-011304_at_[hidden])
Date: 2004-11-24 09:31:02

I have a class that needs to react to a particular signal.  However, the
manner in which it handles the signal is state dependent.  I would,
therefore, like to change the connected slot when necessary.  In
general, this is not a problem.  However, changing the connection inside
another slot is problematic.  For example, assume that Foo::bar() is
already connected to signal_, and signal_() is called...

void
Foo::
bar()
{
  std::cout << "Foo::bar()\n";
  current_connection_.disconnect();
  current_connection_ = signal_.connect(
      boost::bind(&Foo::bar1, this));
}

void
Foo::
bar1()
{
  std::cout << "Foo::bar1()\n";
}

What I want to happen is that bar() will be called, then it will be
disconnected, and bar1 will then be connected in its place.  For
example, given this calling sequence...

signal_();
signal_();

I expect to see...

Foo::bar()
Foo::bar1()

However, sometimes I may see...

Foo::bar()
Foo::bar1()
Foo::bar1()

because bar1() MAY get connected AFTER the place where bar() used to be
connected, resulting in it also being called for the same signal
invocation.

What I think I want is a way to "replace" a connected slot, without
disturbing anything else...

void
Foo::
bar()
{
  std::cout << "Foo::bar()\n";
  current_connection_.replace_slot(&Foo::bar1, this);
}

This is especially important if the slot is originally connected with...

signal_.connect(
    invocation_level, 
    boost::bind(&Foo::bar1, this));

because I see no way to retrieve the ordering information from the
connection.

In any event, how do you suggest I "replace" a conected slot, while
still guaranteeing that the "connection" is invoked exactly once?

Thanks!!!