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Advanced Inheritance 563

16

implemented in terms of a PartsList, just as would have been the case with aggrega-

tion. The private inheritance is just a convenience.

Listing 16.6 demonstrates the use of private inheritance by rewriting the PartsCatalog

class as privately derived from PartsList.

LISTING16.6 Private Inheritance

0: //Listing 16.6 demonstrates private inheritance

1: #include <iostream>

2: using namespace std;

3:

4: // **************** Part ************

5:

6: // Abstract base class of parts

7: class Part

8: {

9: public:

10: Part():itsPartNumber(1) {}

11: Part(int PartNumber):

12: itsPartNumber(PartNumber){}

13: virtual ~Part(){}

14: int GetPartNumber() const

15: { return itsPartNumber; }

16: virtual void Display() const =0;

17: private:

18: int itsPartNumber;

19: };

20:

21: // implementation of pure virtual function so that

22: // derived classes can chain up

23: void Part::Display() const

24: {

25: cout << “\nPart Number: “ << itsPartNumber << endl;

26: }

27:

28: // **************** Car Part ************

29:

30: class CarPart : public Part

31: {

32: public:

33: CarPart():itsModelYear(94){}

34: CarPart(int year, int partNumber);

35: virtual void Display() const

36: {

37: Part::Display();

38: cout << “Model Year: “;

39: cout << itsModelYear << endl;

40: }

41: private:

42: int itsModelYear;