Re: [Boost-users] [signals] Painfully simple signals question

From: Douglas Gregor (dgregor_at_[hidden])
Date: 2005-02-07 00:16:36

On Feb 6, 2005, at 10:13 AM, Tony Juricic wrote:

> Shame be where it belongs, after rading documentation, implementation, 
> examples and test code, I am unable to write what should be simple 
> signals code:
>
> ---------------------------------------------
> *.h
>
> typedef boost::function<void (void)> Callback;

You should replace the Callback typedef with:

   typedef boost::signal<void(void)>::slot_type Callback;

That'll make all of the object tracking stuff work properly.

> boost::signal<void (void)> mySignal;
>
> void Signal::Connect(Callback f)
> {
> // iterate over signal slots, if slot equals input f do nothing	
> // otherwise connect f
> }

This operation is not possible with Signals: you can't get at the 
individual slots once they're connected. Essentially, Signals was 
designed with the idea that comparing function objects for equality 
when connecting/disconnecting is a bad idea, because it breaks down 
when the function objects you build are non-trivial (because it becomes 
hard to duplicate the function object when calling disconnect()).

        Doug