C3766 when deriving a class and interface

Question

Hi,

I have a Windows Runtime Component C++/CX project and while trying to compile this piece of code:

    public interface class IAaa
    {
        void MethodA ();
    };

    public interface class IBbb : IAaa
    {
        void MethodB ();
    };

    ref class Aaa : IAaa
    {
    public:
        virtual void MethodA () { }
    };

    ref class Bbb : public Aaa, IBbb
    {
    public:
        virtual void MethodB () { }
    };

I get this error message:

error C3766: Bbb must provide an implementation for the interface method 'void IAaa::MethodA(void)'

The same code compiles just fine in C#. Is there something wrong with the code of could this be a compiler bug?

Thanks

Answer 1

Hi,

Based on this document, class Bbb must implement MethodB and MethodA.

Please check the Interface Inheritance hierarchies section
http://msdn.microsoft.com/en-us/library/windows/apps/hh755792.aspx

Best regards,
Jesse

---

Jesse Jiang [MSFT]
MSDN Community Support | Feedback to us

Answer 2

Well, the document says:

If interface B inherits from interface A, and ref class C inherits from B, C must implement both A and B. 

And this is clear. However in my case class Aaa already implements MethodA and class Bbb inherits it. Currently I have this workaround:

    ref class Bbb : public Aaa, IBbb
    {
    public:
        virtual void MethodA () override { Aaa::MethodA (); }
        virtual void MethodB () { }
    };