Question

I want to make a very generic pure virtual class i_BIS_Data that will be inherited by unique BIS_Data classes.

class i_BIS_Data
{
public:

i_BIS_Data(void) { }
virtual ~i_BIS_Data( void ) { }

  virtual void setData(bis_data data) = 0;
};

I want all my children of i_BIS_Data to define the bis_data struct as they all will be different. I expect my child class to look similar to the following:

class BIS_0192_Aircraft_ID_Data : i_BIS_Data
{
  public:

  struct bis_data
  {
   UInt16  acid; 
   UInt16  parity; 
  };

  void setData(bis_data data){   m_data.parity = data.parity; 
                             m_data.acid   = data.acid; }
}

When I try to compile a class that uses BIS_0192_Aircraft_ID_Data, I get the following error: error C2061: syntax error: identifier ‘bis_data’. I believe its because I haven’t defined bis_data within the parent class.

So is it possible to “overload” the structure and allow multiple children classes to define what bis_data is?

Answer 1

 template<typename BIS_DATA_T>
 class i_BIS_Data
 {
      typedef BIS_DATA_T bis_data;
      ...
      virtual void setData(bis_data data) = 0;
 };

 struct bis_0192_data
 {
    UInt16  acid; 
    UInt16  parity; 
 };

 class BIS_0192_Aircraft_ID_Data : public i_BIS_Data<bis_0192_data>
 {
   public:
   void setData(bis_data data){   m_data.parity = data.parity; 
                         m_data.acid   = data.acid; }
 };

This should work, however subclasses of i_BIS_Data<XX> with different types for XX are incompatible.