[fpc-devel] "Signals"

[Michael Van Canneyt]

On Fri, 26 Sep 2014, Michael Schnell wrote:

> Yesterday, I had a discussion with a colleague about programming languages.
>
> He said that he did not like Object-Pascal / fpc because it lacks the concept 
> of "signals" he finds in other languages / libraries. (He is not an expert 
> but discusses on base of rumors he collected.)
>
> With "signals" he meant a kind of multi-target events.
>
> He described that multiple parts (units) of a program (or even units within a 
> set of sunning programs) can "subscribe" to a signal (or several of them), 
> and whenever anyone "rises" a signal all subscribers get notified and can 
> react.
>
> Seemingly the execution line in such a "unit" might be as well the main 
> thread or a worker-thread (or even another task/program) and the event 
> handler can be defined to work on this thread (he did not elaborate if always 
> or optionally a newly created thread can be used).
>
> Unfortunately I was not able to come up with a similarly powerful concept 
> available in fpc.

You can use the Observer pattern; it is in the classes unit.

And to be honest, this is not a language concept, but a library concept. 
It can be easily implemented.

Michael.