On 1/26/16 8:58 AM, Jacob Carlborg wrote:
On 2016-01-26 13:59, Manu via Digitalmars-d wrote:
Hmmm. I wonder if this will cause problems...
Is it impossible to support a C++ class implementing a D interface?
No that I know how the C++ compatibility works but I would guess the
compiler needs to know at compile time how to call a method. If it would
be possible to implement a D interface as either a D class or C++ class.
The compiler cannot know which runtime type a variable which is declared
as an interface can hold.
interface A { void foo(); }
class B : A { void foo(); }
extern(C++) class C : A { void foo(); } // assuming this works
A a = new B;
A b = new C; // assuming this works
a.foo();
b.foo();
When the compiler sees "a" or "b", how should it know it should call
"foo" as a D method or C++ method? It only knows about the static type
which is A, a D interface.
The short answer to this question is, no you cannot. The layouts are
different. It's why I have always said, D interfaces should implicitly
convert to Object and support all Object methods. Only D classes can
implement D interfaces.
-Steve
