using a vector of user defined objects

[JamesKidder]

I'm trying to make a customized storage vector for my application but keep getting errors at my vector declaration. I searched around and found that it might be caused by lacking certain item functions (assignment and copy). Unfortunately those are having problems as well.


Here's the header I am concerned with:

#include<string>
#include<fstream>
//I know, don't do this in a header, but at this point I am just trying to get it to work
using namespace std;
class item
{
    public:
    /*
    This constructor accepts a string and creates an object with that name
    @parameter- inputName: The name of the of the item
    */
    item(string inputName);

    /*
    This function intializes a blank object
    */
    item();
    /*
    This function returns the name of the item
    @return: The name of the item
    */
    string getName();
    /*
    This function outputs the members of item
    @param stream: The stream the output is being written to
    @param inputItem:  The item that is being written to the stream
    @return: The outputstream
    */
    friend ostream &operator<<(ostream &stream, item inputItem);
    /*
    this function outputs the size of the name string followed by the name of the item to the stream given
    @param outputStream:  The stream to be written to
    */
    void save(ofstream &outputStream);
    /*
    This function inputs the size of the name vector and then loads the name vector
    @param inputStream: the file stream to be read from
    @return: Whether the load was successful or not
    */
    bool load(ifstream &inputStream);


    /*
    This function constructs an item with the contents of another item
    @param inputItem: The item to be copied from
    */
    item(item const& inputItem);
    
    /*
    This operator assigns the values of another item to itself and returns a pointer to itself
    @param inputItem:  The item the values are being taken from
    @return:  a pointer to this item
    */
    item& operator = (item &inputItem);
    private:
    string name;
};


    /*
    This constructor accepts a string and creates an object with that name
    @parameter- inputName: The name of the of the item
    */
item::item(string inputName)
{
    name=inputName;
}

    /*
    This function intializes a blank object
    */
    item::item()
{
}

    /*
    This function returns the name of the item
    @return: The name of the item
    */
string item::getName()
{
    return name;
}
    /*
    This function outputs the members of item, first the length of the vector and then the vector name
    @param stream: The stream the output is being written to
    @param inputItem:  The item that is being written to the stream
    @return: The outputstream
    */
ostream &operator<<(ostream &stream, item inputItem)
{
    stream<<inputItem.name.length() << inputItem.name;
    return stream;
}

 /*
    this function outputs the size of the name string followed by the name of the item to the stream given
    @param outputStream:  The stream to be written to
    */
void item::save(ofstream &outputStream)
{
    outputStream << *this;
}
    /*
    This function inputs the size of the name vector and then loads the name vector
    @param inputStream: the file stream to be read from
    @return: Whether the load was successful or not
    */
    bool item::load(ifstream &inputStream)
    {
        int i;
        char ch;
        if(inputStream)
        {
            inputStream>>i;
        }
        else
        {
            return false;
        }
        for(int ii=0; ii<i && inputStream; ii++)
        {
            inputStream.get(ch);
            name.push_back(ch);
        }
        if(i!=name.length())
        {
            return false;
        }
        else
        {
            return true;
        }
    }

    /*
    This function constructs an item with the contents of another item
    @param inputItem: The item to be copied from
    */
    item::item(item const& inputItem)
    {
    name=inputItem.getName();
    }
    
    /*
    This operator assigns the values of another item to itself and returns a pointer to itself
    @param inputItem:  The item the values are being taken from
    @return:  a pointer to this item
    */
    item& item::operator = (item &inputItem)
    {
    name=inputItem.getName();
    return this*;
    }





//This is a menu made of items
class itemMenu
{
public:
/*
This function loads all of the items in the file and saves them in the listOfItems
@Param inputStream: The file stream that the items are to be read from
*/
itemMenu(ifstream &inputStream);
/*
This loads an empty menu
*/
itemMenu();
/*
This function adds an item to the listOfItems
@param inputItem: the item to be added
*/
void addItem(item inputItem);
/*
This function erases the item with the given name in the listOfItems
@param itemName: The name of the item to be deleted
*/ 
void deleteItem(string itemName);

/*
This function erases the last item on the menu
*/
void deleteItem();

/*
This function couts all of the items in the listOfItems
*/
void showItems();

/*
This function saves all of the items in the listOfItems
@param outputStream: The file stream for the items to be saved to
*/
void saveMenu(ofstream &outputStream);

/*
This function returns a copy of an item in the menu and a blank item if the index is wrong
@param inputIndex:  The index of the item to be accessed
*/
item getItem(int inputIndex);
private:
vector<item> listOfItems;

};



/*
This function loads all of the items in the file and saves them in the listOfItems
@Param inputStream: The file stream that the items are to be read from
*/
itemMenu::itemMenu(ifstream &inputStream)
{
listOfItems.push_back();
while(listOfItems[listOfItems.size-1].load(inputStream))
{
listOfItems.push_back();
}
listOfItems.pop_back();
}
/*
This loads an empty menu
*/
itemMenu::itemMenu()
{
}
/*
This function adds an item to the listOfItems
@param inputItem: the item to be added
*/
void itemMenu::addItem(item inputItem)
{
listOfItems.push_back(inputItem.getName());
}
/*
This function erases the item with the given name in the listOfItems
@param itemName: The name of the item to be deleted
*/ 
void itemMenu::deleteItem(string itemName)
{
for(int i=0; i<listOfItems.size(); i++)
{
if(listOfItems[i].getName()==itemName)
{
listOfItems.erase(listOfItems.begin()+i-1);
}
}
}

/*
This function erases the last item on the menu
*/
void itemMenu::deleteItem()
{
listOfItems.pop_back();
}

/*
This function couts all of the items in the listOfItems
*/
void itemMenu::showItems()
{
for(int i=0; i<listOfItems.size(); i++)
{
cout << listOfItems[i];
}
}

/*
This function saves all of the items in the listOfItems
@param outputStream: The file stream for the items to be saved to
*/
void itemMenu::saveMenu(ofstream &outputStream)
{
for(int i=0; i<listOfItems.size(); i++)
{
listOfItems[i].save(outputStream);
}
}

/*
This function returns a copy of an item in the menu and a blank item if the index is wrong
@param inputIndex:  The index of the item to be accessed
*/
item itemMenu::getItem(int inputIndex)
{
if(inputIndex<listOfItems.size())
{
return listOfItems.at(inputIndex);
}
else
{
item noName();
return noName;
}
}

Here are the errors I get:
In file included from main.cpp:4:
/home/hewhosurvives/c++/order/item.h: In copy constructor ‘item::item(const item&)’:
/home/hewhosurvives/c++/order/item.h:143: error: passing ‘const item’ as ‘this’ argument of ‘std::string item::getName()’ discards qualifiers
/home/hewhosurvives/c++/order/item.h: In member function ‘item& item:perator=(item&)’:
/home/hewhosurvives/c++/order/item.h:154: error: expected primary-expression before ‘;’ token
/home/hewhosurvives/c++/order/item.h: At global scope:
/home/hewhosurvives/c++/order/item.h:207: error: ISO C++ forbids declaration of ‘vector’ with no type
/home/hewhosurvives/c++/order/item.h:207: error: expected ‘;’ before ‘<’ token
/home/hewhosurvives/c++/order/item.h: In constructor ‘itemMenu::itemMenu(std::ifstream&)’:
/home/hewhosurvives/c++/order/item.h:219: error: ‘listOfItems’ was not declared in this scope
/home/hewhosurvives/c++/order/item.h: In member function ‘void itemMenu::addItem(item)’:
/home/hewhosurvives/c++/order/item.h:238: error: ‘listOfItems’ was not declared in this scope
/home/hewhosurvives/c++/order/item.h: In member function ‘void itemMenu::deleteItem(std::string)’:
/home/hewhosurvives/c++/order/item.h:246: error: ‘listOfItems’ was not declared in this scope
/home/hewhosurvives/c++/order/item.h: In member function ‘void itemMenu::deleteItem()’:
/home/hewhosurvives/c++/order/item.h:260: error: ‘listOfItems’ was not declared in this scope
/home/hewhosurvives/c++/order/item.h: In member function ‘void itemMenu::showItems()’:
/home/hewhosurvives/c++/order/item.h:268: error: ‘listOfItems’ was not declared in this scope
/home/hewhosurvives/c++/order/item.h: In member function ‘void itemMenu::saveMenu(std:fstream&)’:
/home/hewhosurvives/c++/order/item.h:280: error: ‘listOfItems’ was not declared in this scope
/home/hewhosurvives/c++/order/item.h: In member function ‘item itemMenu::getItem(int)’:
/home/hewhosurvives/c++/order/item.h:292: error: ‘listOfItems’ was not declared in this scope
/home/hewhosurvives/c++/order/item.h:299: error: conversion from ‘item (*)()’ to non-scalar type ‘item’ requested
main.cpp: In function ‘int main(int, char**)’:
main.cpp:17: error: ‘orderMenu’ was not declared in this scope
main.cpp:17: error: expected `;' before ‘menu’
main.cpp:18: error: ‘menu’ was not declared in this scope

Any ideas?

[Elysia]

The problem is that a function tries to call a non-const function on a const object.
It's in the item(const item&) (copy constructor). All functions that does not modify the state of the object should be const. So getName should be const since it does not modify the object.

[anon]

The first errors are related to inconsistency in using the const keyword. In particular, getName should be a const method:

string getName() const;

Otherwise you can't call it with a constant object (as you have in the copy constructor).

Another thing is operator=, which should also take a const reference (not modify the right-hand value). Also look at what and how you are returning.

(Further, if your copy constructor/operator= don't do anything else than memberwise assignment, you shouldn't bother implementing them at all - the compiler will produce ones that do exactly that on its own.)

Then a lot of errors might be caused by not including <vector>.

[JamesKidder]

Thanks, the vector declaration fixed most of the errors. You just fixed something that caused me a lot of frustration.

Thanks again