Suggestion: signal/slot mechanism

[Kristian]

On Sat, 02 Sep 2006 14:20:22 +0300, Lutger <lutger.blijdestijn at gmail.com>  
wrote:
> Kristian wrote:
>> It would be nice if D had a signal/slot mechanism similiar to Qt:
>> http://doc.trolltech.com/4.1/signalsandslots.html
>>  It's an elegant way to handle messages sent between objects. It beats  
>> event table declarations used by other GUI libraries IMHO.
>>  It would make D a lot more appealing language to write GUI  
>> applications. Think of wxWidgets written in D... ;)
[snip]
>
> I agree the signal-slot mechanism is nice, but why must it be supported  
> by a compiler? There a lots of good libraries in C++ for this, such as  
> sigslots, libsigc++ and boost::signals. It is not necessary to have  
> extra preprocessor or language support.
>
> It should be possible to do this in a D library. There already is  
> dcouple at dsource, but it is inactive. I have been working on a  
> signal-slot module myself, the only thing missing now is automatic  
> disconnections of which I am not sure how and if to proceed.


Well, one could ask if it's possible to implement a signal/slot mechanism  
by using a library (or by doing it by yourself), then why none of the GUI  
libraries I'm familiar with do not use it? (Qt uses preprocessor.)


There are several general reasons for a feature being directly supported:

- If a feature is supported by a language, programmers will use it a lot  
more often. Actually it almost certainly guarantees that a feature will be  
used.

- Syntax sugar. Being the part of a language, the syntax is consistent  
with the rest of the statements. This makes the feature (usually) simplier  
and easier to use. At least overall readability is better.

- Compile time errors could be more informative.

- If there is a compiler for a operating system, then the feature is  
automatically supported in that system, of course.

- You can rely on the feature being bug free. (You can make that  
assumption.)


And of course, the S/S mechanism wouldn't look bad at the feature list of  
D. ;)