Signals & Slots

[Lutger]

David B. Held wrote:
> I know much has been said about this topic over the years, and several 
> libraries have been written.  Can anyone summarize the state of the art 
> for S&S in D?  I know there is a std.signals, but I can see that it is 
> not the end of the story...
> 
> Dave

Besides std.signals, there is a S&S implementation in Tango, one in 
Luigi by Bill Baxter and one written by myself (sslot).

There are mostly two differences between these implementations: 
thread-safety and the types of slots that are allowed to connect.
The tango implementation is thread-safe, at the cost of being unable to 
'track' connections. sslot has a thread-safe implementation which 
frankly stinks, because it's not really thread-safe at all (deadlock 
possibility in some - documented - circumstances).
The ones in Luigi and sslot are the most generic, and tango's signals 
can also accept functions. std.signals only accepts member functions.

It's not possible in any of the current implementations (that I'm aware 
of) to have both managed or tracked connections and thread-safety. I 
doubt it is possible at all to do in a reasonable efficient manner 
currently. Perhaps when reference counting will come to D.