Interface based programming in C++

This is a small example of the interface I had designed for exposing SkypeKit functions in a DLL .
In the below sample,  only the interface ISkypeClientLib is being exported.

// This interface is exported from the DLL

   1: class SKYPECLIENTLIB_API ISkypeClientLib

   2: {

   3: public:

   4:     virtual bool Connect(char* strAccountUID,char* strAccountPWD) = 0;

   5:     virtual void LogOut() = 0;

   6: };

   7:  

   8: // Forward declaration

   9: class CSkype;

  10:  

  11: class CSkypeClientLib: public ISkypeClientLib

  12: {

  13:     public:

  14:         CSkypeClientLib(void);

  15:         virtual bool Connect(char* strAccountUID,char* strAccountPWD);

  16:         virtual void LogOut();

  17:   

  18:     private :

  19:         CSkype *pSkype ;

  20: // more code

  21:  

  22: }

  23:  

The derived class CSkypeClientLib has the implementations for the functions, but is hidden from the user.

In the main application the user calls the function GetSkypeLibrary( ) , which returns a CSkypeClientLib pointer to the user.

   1: SKYPECLIENTLIB_API ISkypeClientLib* GetSkypeLibrary(void)

   2: {

   3:    ISkypeClientLib *pSkypeLib = new CSkypeClientLib();

   4:    return pSkypeLib;

   5: }

The user can now use the pointer to call the respective functions.

One can further extend the functionality by doing the following

   1: if(riid == __uuidof(CSkypeClientLib))

   2:     return new CSkypeClientLib;

The following figure shows the interface function in Visual Studio 2010 .