First time doing OO

Hey guys, this is my first time using object oriented programming and I'm having a little bit of trouble. I'm trying to create a "Store" class that feeds off my "inventory" class which I have already created. I have to make four member functions: 1) add an inventory item 2) search for an inventory item 3) delete and inventory item 4) show quantity, cost of each inventory item 5) modify an inventory item. I have started it but am stuck on how to modify the item. I have attached all of the programs. The prog6.cpp is the driver for my inventory class.

store.h

Code:

#ifndef Store_H
#define Store_H

#include "inventory.h"
#include <string>

using namespace std;

class Store
{
      public:
             static const unsigned SIZE = 500;
             
      //  Constructors
        Store();
        Store(string ID2 , unsigned quantity , double cost);
        
      // Modification Member Functions
        void loadInventory ( const inventory &a );
        string searchInventory ( string ID2 );
        void modInventory ( string ID2, unsigned quantity, double cost );
        void removeInventory ( string ID2 , inventory &a );
        double showSum () const ;
        
        Private:
                
      //  Member Variables 
        inventory store;
        inventory item[SIZE];
        unsigned size;
};

#endif 

I'll assume those last couple lines being missing from the file is a typo. Also, Private should be private. SIZE cannot be initialized in the manner you have. As a static member, you would need to create and initialize the member variable in the store.cpp file. You would also need a change to how your inventory array was declared. You'd need to make it a pointer instead of an array and dynamically allocate space for it in the constructor and free it in the destructor. I would therefore strongly suggest using an STL container class such as list or vector which would make adding and deleting items easier to deal with and far more flexible than any standard array or pointer. You'd also be able to get rid of the SIZE and size data members since the container would be able to tell you itself how many items it was holding at any given time.




store.cpp

Code:

#include <iostream>
#include <iomanip>
#include <ctype.h>
#include "Store.h"

using namespace std;

// Constructors

Store::Store() { size=0;}

Store::Store(string ID2, unsigned quantity, double cost)
{
     store.setInventory(ID2, quantity, cost);
       size=0;
}

//Constant Member Functions

void Store::loadInventory (const inventory &a )
{
     item[size++] = a;
}

string Store::searchInventory () const
{
       string search;
       cout << "Which product are you searching for?" << endl;
       cin >> search ;
       while (search != ID2)
       {
             item[size++];
       }return search;
}

void Store::modInventory ( unsigned quantity, double cost );
{
     char choice;
     unsigned quantity = 0;
     double cost = 0;
     
     cout << "Do you want to change to price of item? Y/N" << endl;
     cin >> choice;
     if choice = 'Y' or 'y'
     (

Again, is the fact you seem to be chopping off source code at the bottom merely a typo? There is a difference between = and ==. The above if test should be if( choice == 'y' || choice == 'Y' ). In the above while loop where you do search != ID2 there is no ID2 variable in scope. The inclusion of a second constructor doesn't seem to do anything. You initialize the store member variable but don't add it to the array (size is still 0)? A better way to initialize the store member would be to use an initialization list. The second constructor could be rewritten (if it really was necessary) as this:

Code:

Store::Store(string ID2, unsigned quantity, double cost) : store(ID2,quantity,cost), size(0)
{
     // Don't need to do anything here since it's already been done in the initialization list.
}

inventory.cpp

Code:

#include "inventory.h"
#include <iostream>
using namespace std;



    
    inventory::inventory()
    {
         ID = "UNDEFINED" ;
         quantity = 0;
         cost = 0;
    }
    void inventory::setString(string ID2)
    {
         ID2 = "A";
         
    }
    void inventory::setInventory(string ID2, unsigned quantity, double cost)
    {
         setString(ID2);
         setQuantity(quantity);
         setCost(cost);
    }

Did you mean ID = ID2;? The above line as it stands does nothing. It will modify the local copy of ID2 to "A" and then when the function exits, the value will be thrown away as the variable is popped off the stack and nothing will have changed in the inventory object itself. A better name for the function might be setID. Also, you're still missing the rest of the functions in the source file, where are they? Is this another typo or simple omission of code?

Originally Posted by Kross7

I have started it but am stuck on how to modify the item.

Based on the code attached, it would seem you're stuck on just about everything since I see nothing to get user input for new inventory items and add it to a store's inventory list. Start with that, show us some code that gets user input and adds an inventory item to the store. Then we can move on from there to removing an item.

Ok I think I fixed all of those little things you mentioned except for the whole pointer thing that had to do with me declaring my SIZE constant. The one major thing I am having trouble with is my searchInventory, removeInventory and modInventory because I'm not quite sure how to sort through the array searching for a string. Does that make sense? I have also added a new file to act as my driver for the store class.

Code:

//Instead of this
static const unsigned SIZE = 500;
//Try this
enum {SIZE = 500};

Ok I tried the

Code:

 enum { SIZE = 500};

but I still ned help on sortingt through my array using strings. Any ideas or help would be greatly appreciated.

Thanks

Originally Posted by hk_mp5kpdw

Code:

   static const unsigned SIZE = 500;

SIZE cannot be initialized in the manner you have. As a static member, you would need to create and initialize the member variable in the store.cpp file.

Not true. Static constant integral members can be initialised in the header for this very reason.

Originally Posted by c++ standard 9.4.2.4

If a static data member is of const integral or const enumeration type, its declaration in the class definition can specify a constant-initializer which shall be an integral constant expression. In that case, the member can appear in integral constant expressions.

Originally Posted by UMR_Student

Code:

//Instead of this
static const unsigned SIZE = 500;
//Try this
enum {SIZE = 500};

you can do this, but it's not necessary. Personally, I think it's bad style (it was originally a hack to get around the lack of static constant integrals), but it works.

Originally Posted by Kross7

but I still ned help on sortingt through my array using strings. Any ideas or help would be greatly appreciated.

Can you be a bit more specific? What do you mean by "sortingt through my array using strings"?

Yea, the project I am doing calls for three functions. One to search through an array of objects, one to remove items from the array and one to modify items in the array. I'm wondering how to get to the different items in an array using a for loop, but I don't know what to label the item in the loop. The only real way to search for the item is by its ID which I think is a variable named ID2 which is a string.

You probably want a std::map. check out the stl link in my sig

The class im taking does not let us use functions we havent learned yet so i can't use that. We are only supposed to use the functions i have labeled in my store.h file, if that makes sense. Any other suggestions?

the best thing about OO is that it pushed you (C++ programmer) to your limits, cuz u have to do extra work like assignment operator and copy constructor if you have dataon the heap and stuff.
keep up the great work