"cannot instantiate abstract class" Multiple inheritance and 3rd party interface - c++

Question

I have an existing project with the following class inheritance
class Base
{
public:
Base();
virtual ~Base();
void SetID(unsigned short);
virtual inline unsigned short GetID();
protected:
unsigned short id;
};
class Generic : public Base {
public:
Generic(const char *in_name);
const char* GetName() { return name; }
protected:
char name[30];
};
class Actor : public Generic
{
public:
Actor(const char *in_name);
~Actor();
void DoSomething(const char* str);
};
Now i created a separate project were i want to provide an interface that has to be implemented in order to use the functionality - i plan on reusing this project for other implementation.
class MyInterface
{
public:
virtual ~MyInterface() {}
// Our methods that need to implemented
virtual const char* GetName() = 0;
virtual void DoSomething(const char* str) = 0;
virtual unsigned short GetID() = 0;
};
Now i simply wanted to use this with my actor class e.g.
class Actor : public Generic, public MyInterface
however it fails to compile
'const char *MyInterface::GetName(void)' : is abstract see declaration of 'MyInterface::GetName'
'unsigned short MyInterface::GetID(void)' : is abstract see declaration of 'MyInterface::GetID'
error C2385: ambiguous access of 'GetName'
could be the 'GetName' in base 'Generic'
or could be the 'GetName' in base 'MyInterface'
The problem is probably that GetName is already implemented in Generic, and GetID is already implemented in Base - so in the child class Actor implementing the Interface is not possible because the compiler is not smart enough to realize there is already an implementation of these methods.
However, i found a workaround - but for this i would have to extend the header of the actor class which is not a nice thing - and i wanted to know if there is another approach - my fix is
class Actor : public Generic, public MyInterface
{
public:
Actor(const char *in_name);
~Actor();
void DoSomething(const char* str);
const char* GetName() { return Generic::GetName(); };
inline unsigned short GetID() { return Base::GetID(); };
};
Now this obviously will not work for varargs methods and i would have to implement existing methods and delegate to the parent again - is there a better solution?
EDIT For clarifications - the classes base,generic and actor exist in another project managed by others, modifications to these should be very limited. - I created a seperate project which creates a static LIB - to use functions of these in conjunction with the actor class - i created an interface to not have any dependency in my own project and also provide a reusable lib for other projects which would simply just need to implement this interface.

Answer 1

class Base
{
protected:
unsigned short id;
public:
void SetID(unsigned short);
virtual inline unsigned short GetID() { return id; }
virtual ~Base() {}
Base(): id() {}
};
class Generic
: public Base
{
protected:
char name[30];
public:
const char* GetName() { return name; }
Generic(const char* in_name): name() {}
};
class Actor
: public Generic
{
public:
void DoSomething(const char* str) {}
~Actor() {}
Actor(const char* in_name)
: Generic( name )
{}
};
class MyInterface
{
public:
// Our methods that need to implemented
virtual const char* name() const = 0;
virtual int id() const = 0;
virtual void doSomething( const char* str ) = 0;
virtual ~MyInterface() {}
};
template< class TpBase >
class MyInterfaceOn
: public virtual MyInterface
, public TpBase
{
public:
typedef TpBase Base;
private:
MyInterfaceOn& mutableSelf() const
{ return *const_cast<MyInterfaceOn*>( this ); }
public:
const char* name() const { return mutableSelf().Base::GetName(); }
int id() const { return mutableSelf().Base::GetID(); }
void doSomething(const char* str) { Base::DoSomething( str ); }
MyInterfaceOn( char const name[] )
: Base( name )
{}
};
class MyActor
: public MyInterfaceOn< Actor >
{
public:
MyActor( char const name[] )
: MyInterfaceOn< Actor >( name )
{}
};
int main()
{
MyInterface const& actor = MyActor( "NN" );
}