Why i cannot create third variable

[Felicia123]

#include <iostream>
#include <string>

using namespace std;

class Vending{
private:
	string item[4];
	double coin;
public:

	Vending();

	void showItemMenu();
	void insertCoin();
	void buyItem();
};

vending.h

#include "vending.h"

Vending::Vending() {
    coin = 0.00;
    item[0] = "Coffee";
    item[1] = "Snack";
    item[2] = "Cans of soda";
    item[3] = "hot drinks";
    item[4] = "ice cream";
    
}

void Vending::showItemMenu(){
    cout << "\tWelcome to Lim's Vending Machine" << endl
         << "--------------------------------------------------" << endl;
    for( int i = 0 ; i < 5 ; i++ ){
        cout << ( i+1 ) << ". " << item[i] << endl;
    }
}

void Vending::insertCoin(){
    cout << "Please insert RM 5 for each item : RM";
    double money = 0.00;
    double moremoney = 0.00;
    double tmp = 0.00;
    cin  >> money;
    if( money < 5 && money > 0 ){
        do{
            tmp = 5 - money;
            cout << "Please insert more RM" << tmp << " !" << endl
                 << "Insert more money : RM";
            cin  >> moremoney;
            money+= moremoney;
   
        }while( money < 5 && money > 0);
        if( money > 5 ){
            tmp = 0.00;
            tmp = money - 5;
            cout << "Here is your change : RM" << tmp << endl;
            buyItem();
        }
        else
            buyItem();
    }
    else if( money > 5 ){
        tmp = money - 5;
        cout << "Here is your change : RM" << tmp << endl;
        buyItem();
    }
}

void Vending::buyItem(){
    
    cout << endl;
    cout << "Choose item : ";
    int itemChoice = 0;
    cin  >> itemChoice;
    if( itemChoice < 1 || itemChoice > 5 ){
        do{
            cout <<"Invalid input ! Please re-enter";
            cin  >> itemChoice;
        }while(itemChoice < 1 || itemChoice > 5 );
    }
    switch( itemChoice ){
        case 1:
            cout << "Here is your Coffee" << endl
                 << "Thanks you ! Please come again !" << endl << endl;
            break;
        case 2:
            cout << "Here is your Snack" << endl
                 << "Thanks you ! Please come again !" << endl;
            break;
        case 3:
            cout << "Here is your Soda" << endl
                 << "Thanks you ! Please come again !" << endl;
            break;
        case 4:
            cout << "Here is your hot Drinks" << endl
                 << "Thanks you ! Please come again !" << endl;
            break;
        case 5:
            cout << "Here is your ice cream" << endl
                 << "Thanks you ! Please come again !" << endl;
            break;
        default:
            cout << "Invalid input!";       
    }
}

vending.cpp

/* 
 * File:   main.cpp
 * Author: Lim
 *
 * Created on March 12, 2013, 1:19 PM
 */

#include "vending.h"


int main( ) {

    Vending theVending;
   
    theVending.showItemMenu();
   // theVending.insertCoin();

	system( "pause" );
    return 0;
}

main.cpp


why i cannot create third variable inside my private data

if i create my program will stop run.
else i cannot run.
and why i cannot delete the virtual constructor and the another constructor?

if i delete them my program will stop working window pop out ! my lecturer also cannot solve the program !

[MiiNiPaa]

item[4] = "ice cream";
You accessing out of bounds here. Your item array declared as char item[4][20]; so you can hold 4 c-strings here with indexes 0, 1, 2 and 3.

[Felicia123]

@miniioaa.change it to string.

my default program are string. paste wrong here. but can't work also

[MiiNiPaa]

That will not change fact that you are accessing out of bounds. Even if it is string item[4]; largest index is 3: item[3]

item[4] will access random memory and can corrupt it (write a garbage to another member for example)

[TheIdeasMan]

You should really have a private member:

static const unsigned SIZE = 5;
string item[SIZE];

rather than 5 everywhere throughout your code.

Line 17 in the showItemMenu function segfaults because you add 1 in the body of the loop - which takes you out of bounds for the array again.

In the insertCoin function be careful comparing doubles - you loops might not run the correct number of times, because of the way that doubles are stored.

I also don't like do loops, because you have the test twice on lines 28 & 35 and 58 & 62.

It doesn't make sense for the if on lines 36 to 41 to be inside the If on line 27 because it will never be true & is unreachable code. You have it duplicated on lines 45 - 49.

Also a quit option in your switch.

If you enclose the switch in a while loop that uses bool Quit variable, bad input can be dealt with by the default clause.

HTH