Abstract class de/con-structor problem

Hi all,

I have tried to make an abstract class in the file Cat.h that already contains the class Cat, but I cant get the Cat class to extend the Abstract cat class. My goal is to make an interface for the Cat class.
Cat.h:

Code:

---

/**
Enumerator for cat object types
*/
typedef enum {
  cob_Male,
  cob_Female,
  cob_NeuMale,
  cob_NeuFemale
} Cat_Object;
       
typedef enum
{
      Cat_InitialState,
      Cat_Movement,
          Cat_ReproBehaviour
} TypeOfCatState;

class Abstract_Cat : public TAnimal
{
public:
        Abstract_Cat();
        virtual        ~Abstract_Cat();

        virtual void BeginStep      (void) = 0;
                ...
        virtual int EvaluateBestDirection() = 0;
};

class Cat : public Abstract_Cat
{
public:
        Cat(int a_x, int a_y, Landscape * p_L, Cat_Population_Manager* p_PPM);
        virtual ~Cat(void);

protected:
        //variables
        Cat_Population_Manager* m_OurPopulationManager;
        ...
        int StepsSoFarWithoutGoingHome;
        TypeOfCatState m_CurrentCState;
       
        //lists
        int QualityScoreArray[8]; //array for keeping the score values for each direction (0-7) - method:EvaluateBestDirection()
        vector<int> BestDirectionsList; //list for holding directions with the highest score
       
        //methods
        virtual void BeginStep      (void);
                ...
        int EvaluateBestDirection();
};

class struct_Cat
{
        public:       
                int x;
                int y;
                Landscape* L;
                Cat_Population_Manager* CM;       
};

---

Error:
1>Cat.obj : error LNK2019: unresolved external symbol "public: virtual __thiscall Abstract_Cat::~Abstract_Cat(void)" (??1Abstract_Cat@@UAE@XZ) referenced in function "public: virtual __thiscall Cat::~Cat(void)" (??1Cat@@UAE@XZ)
1>Cat.obj : error LNK2019: unresolved external symbol "public: __thiscall Abstract_Cat::Abstract_Cat(void)" (??0Abstract_Cat@@QAE@XZ) referenced in function "public: __thiscall Cat::Cat(int,int,class Landscape *,class Cat_Population_Manager *)" (??0Cat@@QAE@HHPAVLandscape@@PAVCat_Population_Man ager@@@Z)
1>.\vc_mswd\almass.exe : fatal error LNK1120: 2 unresolved externals
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

And if i remove the constructor in class Abstract_Cat (Abstract_Cat();)) then i get an error message that says a cannot instantiate objects of an abstract class.

You need to implement the constructors and destructors for Abstract_Cat, not just declare them.

I also don't see a declaration for TAnimal.

Thank you, i just added this part to Cat.cpp and it works.

Code:

---

Abstract_Cat::Abstract_Cat(int a_x, int a_y, Landscape * p_L, Cat_Population_Manager* p_PPM) : TAnimal(a_x,a_y,p_L)
{
}

Abstract_Cat::~Abstract_Cat()
{
}

---

thanks a lot :-)