How to dispatch a class function for an object accessed by handle?

[wjoe]

On Friday, 6 March 2020 at 14:14:04 UTC, Adam D. Ruppe wrote:
> On Friday, 6 March 2020 at 14:05:55 UTC, Steven Schveighoffer 
> wrote:
>> Adam's way doesn't work either, because the call doesn't use 
>> the alias, but just instantiates opDispatch with the new name!'
>
> oh yikes, how did I not notice that?!
>
> so yeah just kinda screwed. I'd probably suggest at tis point 
> having the opDispatch be a trivial implementation that just 
> forwards to another named method.
>
> struct A {
>   template opDispatch(string name) {
>      auto opDispatch(T, Args...)(Args args) {
>            return other_name!(name, T, Args)(args);
>      }
>   }
>
>   auto other_name(string name, T, Args...)(Args args) {
>       // real implementation
>   }
> }
>
>
> and then to test it externally you do
>
> a.other_name!("whatever", Bitmap)(args, here);

This isn't the worst thing to use and since it's just for testing 
it's fine.

I came up with a similar interface like a.other_name!("whatever", 
Bitmap)(args, here); after discarding .opDispatch() and I called 
the thing
  .dispatch(T, string fn, ARGS...)(...).

But didn't like the string part and that's when I introduced the 
alias fn because I figured maybe it's possible to do something 
like:
   factory.dispatch!(Bitmap.load)(handle, path);
and get the Bitmap part from that alias and hence save the 
duplicate Bitmap type in factory.dispatch!(Bitmap, 
Bitmap.load)(...);

Anyways thanks for your help.