Hello betterC people. I have done this little project for anyone wanting to use classes in betterC without losing interface implementations for them.

The library simply defines CppExtend and CppInterface as objects which you must extend. It has a simple allocator New!T and deallocator Destroy!T.

It works by defining and redefining functions based on inputs. The classes implementations are private inside the class, it stores each implementation with a reference to base class to call the base class implementation of the functions, so, you can get a standalone interface like we have in pure D today.

Simple example code to stoke your curiosity:

extern(C++)
{
	///Interface
	abstract class Printable
	{
		void print();
	}
	///Interface
	abstract class Stringificable
	{
		extern(D) string toString2();
	}


	///New class implementing Printable and Stringificable classes
	class Test : CppInterface!(Test, Printable, Stringificable)
	{
		void print()
		{
			import core.stdc.stdio;
			printf("toString on print function: %s\n", toString2.ptr);
		}
		extern(D) string toString2()
		{
			return __traits(identifier, Test);
		}
	}
}

extern(C) void main()
{
    Test t = New!Test;
    t.print();
    Printable p = t.getInterface!Printable;
    p.print();
}

I have tested it under DLL boundaries, it is working correctly. I have worked on this project as a future intention of checking into how I'm going to make my game engine betterC compatible.

Requires dmd-fe 2.101 or later

https://code.dlang.org/packages/betterc-interface