Question

I have a problem with Visual C++ 2005, where apparently inner classes with the same name but in different outer classes are confused.

The problem occurs for two layers, where each layer has a listener interface as an inner class. B is a listener of A, and has its own listener in a third layer above it (not shown).

The structure of the code looks like this:

A.h

class A
{
public:
    class Listener
    {
    public:
        Listener();
        virtual ~Listener() = 0;
    };
    // ...
};

B.h

class B : public A::Listener
{
    class Listener
    {
    public:
        Listener();
        virtual ~Listener() = 0;
    };
    // ...
};

A::Listener() and A::~Listener() are defined in A.cpp.

B.cpp

B::Listener::Listener() {}
B::Listener::~Listener() {}

I get the error

B.cpp(49) : error C2509: '{ctor}' : member function not declared in 'B'

The C++ compiler for Renesas sh2a has no problem with this, but then it is more liberal than Visual C++ in some other respects, too.

If I rename the listener interfaces to have different names the problem goes away, but I’d like to avoid that (the real class names instead of A or B are rather long).

Is what I’m doing correct C++, or is the complaint by Visual C++ justified?

Is there a way to work around this problem without renaming the listener interfaces?

Answer 1

the code you posted produced the same compiler error you described on my machine. I’m not so sure myself what the problem exactly is, but I have a feeling that inherting from a pure virtual class and declaring a pure virtual class within the descendant might not be a good idea.

I managed to compile a modified version, maybe this helps you solve your problems:

class OuterA
{
  public:
    class Listener
    {
      public:
        Listener() {}
        virtual ~Listener() = 0 {}
    };

    OuterA() {}
    ~OuterA(){}
};

class OuterB : public OuterA::Listener
{
  public:
    class Listener
    {
      public:
        Listener()  {}
        ~Listener() {}
    };

    OuterB()  {}
    ~OuterB() {}
};

// EDIT to avoid inline ctor and dtor

If you use typedefs to hide the names of the Listeners at least my demo code compiles and links:

// header

class OuterA
{
  public:
    class Listener
    {
      public:
        Listener();
        virtual ~Listener() = 0;
    };

    OuterA();
    ~OuterA();
};   

class OuterB : public OuterA::Listener
{
  public:
    class Listener
    {
      public:
        Listener();
        virtual ~Listener() = 0;
    };

    OuterB();
    ~OuterB();
};

// implementation

OuterA::OuterA(){}
OuterA::~OuterA(){}

OuterA::Listener::Listener(){}
OuterA::Listener::~Listener(){}

typedef OuterB::Listener BListener;

OuterB::OuterB() {}
OuterB::~OuterB(){}

BListener::Listener(){}
BListener::~Listener(){}