Below is a program that has class definitions for Item, Customer and Sales. The main simply creates object object of each class and test its member functions. Modify the main program such that it provides a menu driven interface where user can create objects of Item, Customer and a complete a sales transaction with the sales object.The program should also have an option for display the records of items,customers and sales.To make your program more useful,include file handling such that when objects are created for Items,Customers and Transaction,the user will be prompted to save the recordon the file or not.

here's the code it's not displaying anything pleasee help i'm running it by Dev c

#include <conio.h>
#include <iostream>
#include <string.h>
using namespace std;

class Item {
  int itemCode;

private:
  double price;
  double discount;

protected:
  int qtyOnStock;
  char *name;

public:
  Item() {
    itemCode = 0;
    strcpy(name, "UNKNOWN");
    price = 0;
    discount = 0;
    qtyOnStock = 100;
  }
  void setItemCode(int c) { itemCode = c; }
  int getItemCode() { return itemCode; }
  double getPrice() { return price; }
  void setPrice(double p) { price = p; }
  void setDiscount(double d) { discount = d; }
  double getDiscount(double d) { return ((d < 20 ? d : 20) / 100 * price); }
  void setName(char *n) { name = n; }
  char *getName() { return name; }

  void setQtyOnStock(int q) { qtyOnStock = q; }
  int getQtyOnStock() { return qtyOnStock; }
};
class Customer {
private:
  int id;
  char *name;
  char *contactNo;
  int type;

public:
  Customer() {
    id = 0;
    strcpy(contactNo, "No Num");
    strcpy(name, "No Name");
    type = 0;
  }
  void setId(int newId) { id = newId; }
  int getId() { return id; }
  void setName(char *n) { strcpy(name, n); }
  char *getName() { return name; }
  void setContactNo(char *c) { strcpy(contactNo, c); }
  char *getContactNo() { return name; }
};
class Sales {
private:
  Item item;
  Customer cust;
  char *date;
  int qtySold;

public:
  Sales() { date = "mm-dd-yyyy"; }
  void setItem(Item newItem) { item = newItem; }
  Item getItem() { return item; }
  void setCustomer(Customer newCust) { cust = newCust; }
  Customer getCustomer() { return cust; }
  void setDate(char *newDate) { strcpy(date, newDate); }
  char *getDate() { return date; }
  void setQtySold(int newQty) { qtySold = newQty; }
  int getQtySold() { return qtySold; }
};
int main() {
  Item item1;
  Customer cust1;
  Sales sales1;
  item1.setItemCode(143);
  item1.setName("Ballpen");
  item1.setPrice(12.5);
  item1.setQtyOnStock(250);
  cust1.setId(123);
  cust1.setName("Juan dela Cruz");
  sales1.setItem(item1);
  sales1.setCustomer(cust1);
  sales1.setDate("10-27-2018");
  sales1.setQtySold(98);
  item1.setQtyOnStock(item1.getQtyOnStock() - sales1.getQtySold());
  system("cls");
  cout << sales1.getItem().getName() << endl << item1.getQtyOnStock();
  getch();
  return 0;
}

CodePudding user response：

In your Item class

protected:
  int qtyOnStock;
  char *name;

public:
  Item() {
    itemCode = 0;
    strcpy(name, "UNKNOWN");
    price = 0;
    discount = 0;
    qtyOnStock = 100;
  }

name is an unitialized char pointer so copying to it will result in UB.

change char* name to std::string name, replace strcpy(...) name = "UNKNOWN"

Normally though you initialize member variables like this

  Item() 
  : itemCode(0), itemCode(0), name("UNKNOWN"), price(0), discount(0), qtyOnStrock(100) 
  {}

a newer compiler lets you initialize in other ways like when declared e.g.

protected:
  int qtyOnStock{100};
  std::string name{"UNKNOWN"};
...

CodePudding user response：

The main and biggest proble is that you do C-style string handling with char* and even that in a wrong way.

If you would enable all warning in your compiler, it would already tell you the problems. My VS2019 gives 15 errors, 1 warning and 7 messages, when I try to compile your code. Please see:

So, the main problem is that you are using char* that are not initialzed, meaning they point to somehwere, and that you do not allocate memory to store your strings.

So all your strcpy functions will fail and probably crash your system. Also the assignments to a char* will fail in most cases.

You will overwrite some random memory.

All this can be immediately fixed, without big problems, if you would use std::string instead of char*. Because char* are that error prone, C introduced the std::string, so, please use it.

Sometimes you have C teachers that want you to use char*. Those teachers should be fired. But if you really need to use char*. Then you must allocate memory, before coping data.

Let us assume that you have a string "myName" and you want to copy that.

char* name{};
name = new char[strlen(myName) 1];  //  1 for the trailing '\0'
strcpy(name, myName);

// ...
// ...
// Do stuff
// ...
// ...

delete [] name;  // Release memory at the end

But as said. Simply use std::string

Your program as is, cannot work. You need a major refactoring.