2.7 Object manipulation - inheritance  (Page 3/7)

Example

//Stocks_02.h

class Stocks {

public:

Stocks(char* szName);

~Stocks(); //destructor

void setStockName(char* szName);

char* getStockName();

void setNumShares(int);

int getNumShares(int);

void setPricePerShare(double);

double getPricePerShar();

double calcTotalValue();

private:

char* szStockName;

int iNumShares;

double dCurrentValue;

double dPricePerShare;

};

//Stocks.cpp

#include “stocks_02.h”

#include<string.h>

#include<iostream.h>

Stocks::Stocks(char* szName){

szStockName = new char[25];

strcpy(szStockName, szName);

};

Stocks::~Stocks(){

delete[] szStockName;

cout<<”Destructor called”<<endl;

}

void Stocks::setNumShares(int iShares){

iNumShares = iShares;

}

int Stocks::getNumShares()const{

return iNumShares;

}

void Stocks::setPricePerShare(double dPrice){

dPricePerShare = dPrice;

}

int Stocks::getPricePerShare() const{

return dPricePerShare;

}

void Stocks::setStockName(char* szName){

strcpy(szStockName, szName);

}

char* Stock::getStockName() const{

return szStockName;

}

double Stocks::calcTotalValue(){

dCurrentValue = iNumShares*dPricePerShare;

return dCurrentValue;

}

int main(){

Stocks stockPick1(“Cisco”);

stockPick1.setNumShares(100);

stockPick1.setPricePerShare(68.875);

Stocks* stockPick2 = new Stocks(“Lucent”); //heap object

stockPick2->setNumShares(200);

stockPick2->setPricePerShare(59.5);

cout<<“The current value of your stock in “

<<stockPick1.getStockName()<<“ is $”

<<stockPick1.calcTotalValue()

<<“.”<<endl;

cout<<“The current value of your stock in “

<<stockPick2->getStockName()<<“ is $”

<<stockPick2->calcTotalValue()

<<“.”<<endl;

return 0;

}

The output of the above program:

The current value of your stock in Cisco is $6887.5

The current value of your stock in Lucent is $11900

Destructor called.

Notice that in the above program, the destructor function is called only once. The stockPick1 object calls the destructor when it is destroyed by the main() function going out of scope. The stockPick2 object does not call the destructor since it is declared on the heap and must be deleted manually.

To delete the stockPick2 object manually, add the statement delete stockPick2; to the main() function as in the following program:

int main(){

Stocks stockPick1(“Cisco”);

stockPick1.setNumShares(100);

stockPick1.setPricePerShare(68.875);

Stocks* stockPick2 = new Stocks(“Lucent”); //heap object

stockPick2->setNumShares(200);

stockPick2->setPricePerShare(59.5);

cout<<“The current value of your stock in “

<<stockPick1.getStockName()<<“ is $”

<<stockPick1.calcTotalValue()

<<“.”<<endl;

cout<<“The current value of your stock in “

<<stockPick2->getStockName()<<“ is $”

<<stockPick2->calcTotalValue()

<<“.”<<endl;

delete stockPick2;

return 0;

}

The output of the above program:

The current value of your stock in Cisco is $6887.5

The current value of your stock in Lucent is $11900

Destructor called.

Destructor called.

Constant objects

If you have any type of variable in a program that does not change, you should always use the const keyword to declare the variable as a constant.

To declare an object as constant, place the const keyword in front of the object declaration.