Abstract classes vs interfaces, casting from void*

[Alex]

On Sunday, 11 August 2019 at 16:05:20 UTC, John Colvin wrote:
> I'm trying to narrow down exactly what patterns work with each 
> and how they overlap.
>
> What I was trying to get at with the abstract method thing is 
> that
>
> abstract class C
> {
>     void foo();
> }
>
> is an abstract class with a non-abstract method, whose 
> implementation is going to come from somewhere else (not a 
> common pattern in D).
>
> class C
> {
>     abstract void foo();
> }
>
> is an abstract class with an abstract method foo, which means 
> you have to override it in a inheriting class to get a 
> non-abstract class.

As I see this, everything you wrote is correct. :)

But you compared abstractness with interface usage, initially. 
So... I would say, interfaces are more like the abstract method 
case without any function body. But then, you will have to use 
"override" all across the inherited classes.