Sams Teach Yourself C++ in 21 Days

Working with Advanced Functions 303

10

15: int itsVal;

16: };

17:

18: Counter::Counter():

19: itsVal(0)

20: {}

21:

22: int main()

23: {

24: Counter i;

25: cout << “The value of i is “ << i.GetItsVal() << endl;

26: return 0;

27: }

The value of i is 0

As it stands, this is a pretty useless class. It is defined on lines 6–16. Its only

member variable is an int. The default constructor, which is declared on line 9

and whose implementation is on line 18, initializes the one member variable,itsVal,

to zero.

Unlike an honest, red-blooded int, the Counterobject cannot be incremented, decre-

mented, added, assigned, or otherwise manipulated. In exchange for this, it makes print-

ing its value far more difficult!

Writing an Increment Function ......................................................................

Operator overloading restores much of the functionality that has been stripped out of this

class. Two ways exist, for example, to add the capability to increment a Counterobject.

The first is to write an increment method, as shown in Listing 10.7.

LISTING10.7 Adding an Increment Operator

1: // Listing 10.7 - The Counter class

2:

3: #include <iostream>

4: using namespace std;

5:

6: class Counter

7: {

8: public:

9: Counter();

10: ~Counter(){}

11: int GetItsVal()const { return itsVal; }

OUTPUT

LISTING10.6 continued

ANALYSIS