Signals and Slots in D

[Don Clugston]

Walter Bright wrote:
> Bill Baxter wrote:
>> I think railroading Qt's S&S into a language is the wrong approach. 
>> What goes into the language should be a more general mechanism on top 
>> of which schemes like dynamic S&S can be easily built.
> 
> I agree, and thanks for letting me know about the string matching. 
> That'll become possible in D later when it gets more introspection 
> abilities.

Some thoughts about introspection:

The most basic introspection would simply be, for each class and struct 
Typeinfo, add a pointer to a string that's just a concatenation of names 
and mangled types.
[name]\0[mangleof]\0[name]\0[mangleof]\0...[name]\0[mangleof]\0\0.
Since we have .alignof and .sizeof, this would allow all data members to 
be identified; and would allow code to be developed that could do 
serialization stuff. It would also be reasonably compact.
And an identical treatment for the functions in the vtable (just need to 
maintain the same order of functions). Given a string XXX, you could 
search for a function named "slotXXX" in the manglelist, and call the 
corresponding entry in the vtable.

It wouldn't deal with static functions (where you need the address as 
well as the name and type info)
I guess the challenging issue is to make sure that functions that aren't 
  referenced don't get type info stored? I imagine those dynamic 
languages have trouble discarding unused functions at link time. I think 
you'd need to tell the compiler "don't discard this function even if you 
think it's not used, it's only referenced in a text string".