On Wednesday, 2 April 2014 at 14:23:57 UTC, Ola Fosheim Grøstad
wrote:
On Monday, 24 February 2014 at 08:41:06 UTC, Steve Teale wrote:
>
Yes. This is "inner virtual functions" as opposed to "outer
virtual functions" (C++). The successor to Simula, BETA
(http://daimi.au.dk/~beta/), has this. Simula has this in the
constructor of a class (which syntactically is the body), but
BETA has the concept everywhere:
somefunction:<(#
statements1;
inner;
statements2;
#)
When you specialize a function/class the extra stuff you add is
replacing the "inner" statement (and can provide it's own
"inner").
I had gone some distance along that course. A virtual function to
handle events examined the event to see if it could deal with it.
If it could not, it called a 'specificHandler' virtual function.
But that approach only works if you have a hierarchy of known
depth, when specificHandler only gets called for the leaf classes.
Later, I have had the constructors of derived classes add a
handler delegate to a list of potential handlers maintained in
the base class. The actual handler in the base class is a final
method that simply iterates that list until some derived class
handles the event, or throws if none do.
But both of these approaches are clumsy compared to what I would
like to see.
It would help if D had 'direct' class methods (as opposed to
final or virtual), as then I think it would be more
straightforward to generate the delegate list.
I'm pleased to see though that some other languages have noted
this deficiency.
Steve
