adding multiple things to one vector

Hi,

I'm trying to include multiple things into a vector. My program is suppose to read from an input file that looks something like

add 12345 12.50 50

add - tells me I need to add this to a list, which I'll be using vector
12345 - that's the id number
12.50 - the price
50 - quantity

I'm going to need to use a linear search later if the input file tells me to change the price or quantity but I'm stuck trying to how to add them in the first place. I'm also trying to do this using a class.

Forget about writing code for while and try to work it out on paper.

Start with defining a class using three member variables, one for id number, on for the price and one for the quantity.

Then look up how to use the std::vector class to add items to a vector.

In theory you if the first token in the line is add you will add a new object to the vector if it's id doesn't already exist in the vector and increase the quantity if it does already exist. Similarly, if the first token is remove then you will decrease the quantity or add it to the vector and put in a back order if it doesn't already exist.

Oh... I'm doing that as I go along, writing it down and then putting the code in.

Does anyone know where I can find a sample where it uses vectors and class in one program?

It is really rather easy. vector<MyClass> myVec; myVec.push_back(myClassVar); etc. If you know how to use vector with an int it is not much different with a class.

Did you have any specific problems when you attempted to do it?

Here's some information on vectors. It has all you need on how to add an element to a vector of elements.

http://www.cppreference.com/cppvector/index.html

the std::vector class is templated so all you have to do is put the name of your class in the angle brackets instead of int when you declare the vector:

//declare a vector that will hold elements of type int
std::vector <int> myInts;

just be sure to add the vector header file and use either the std:: prefix before each declaration of a std::vector object or type an appropriate using statement before main() to gain access to the file contents.

Thank you both elad and Daved soooooooo much. At first, when I came to this board, I'm like "oh I'm probably not going to get any help but it's worth a shot," but that's going to help me a lot. And you guys explained it so much better than my professor did...

Can my vector have the follow elements: a string, an int, and a double all in one... vector?

Originally Posted by brooklyn

Can my vector have the follow elements: a string, an int, and a double all in one... vector?

No. When you declare a vector you have to specify the type of elements it holds.
The closest you can get to insert different types of objects is to declare it to hold pointers to a common baseclass.
Kurt

>> Can my vector have the follow elements: a string, an int, and a double all in one... vector?

Yes, but that uses some advanced stuff that you don't need or want (e.g. boost::variant). Based on the description of your problem it makes more sense to combine the data in a class and store instances of the class in your vector.

So I can't do like

Header file:

Code:

public:
	inputnewitemd(string n, int q, double c)	
		:itemNumber(n), quantity(q), cost(c);

cpp file of the class:

Code:

inventoryItem::inputnewitemD( string n, int q, double c )
{
	vector < inventoryItem > inventoryList; //vector to store the inventory item
	inputnewItem a( n, q, c );
	inventoryList.push_back(a);	//adds inventory number to vector
}

because the program will have to change either q and/or c of n after n is added into a vector (q and c of that n will have to be added in too). I'll have to search for n and then change that specific element's q and/or c.

is this what you are trying to do ?

Code:

#include <iostream>
#include <string>
#include <vector>

using namespace std;

class item {

public:
   item( int i_, string s_ ):i(i_), s(s_) {}
   
   void set_i(int i_)  { i = i_; }
   void set_s(string s_)  { s = s_; }
   
   int get_i()  { return i; }
   string get_s()  { return s; }
private:       
   int i;
   string s;        
};


int main() {
    
    vector<item> vec;
    
    vec.push_back( item( 1, "one" ) );
    vec.push_back( item( 2, "two" ) );

    for ( int i = 0; i < vec.size() ; ++i )
        if ( vec[i].get_i() == 2 ) 
            vec[i].set_s("zwei");
                    
    for ( int i = 0; i < vec.size() ; ++i )
        cout << vec[i].get_i() << " " << vec[i].get_s() << endl;
                    
    return 0;
}

Kurt

wow... that is...

Thanks

Your code idea was fine. You have an inventoryItem class that holds the itemNumber, quantity and price. You create a new instance and pass it values for those properties, and then you push that instance on to the vector. The only problems in your posted code are with naming. For some reason you are using inputnewItem instead of inventoryItem as the type of your variable called a, and you used inputnewitemd instead of inventoryItem as the name of your constructor for the inventoryItem class. Fix those and you are on the right track.

Thanks again.

I understood what Zuk did by finding item 2 and replacing zwei with two:

Originally Posted by ZuK

is this what you are trying to do ?

Code:

#include <iostream>
#include <string>
#include <vector>

using namespace std;

class item {

public:
   item( int i_, string s_ ):i(i_), s(s_) {}
   
   void set_i(int i_)  { i = i_; }
   void set_s(string s_)  { s = s_; }
   
   int get_i()  { return i; }
   string get_s()  { return s; }
private:       
   int i;
   string s;        
};


int main() {
    
    vector<item> vec;
    
    vec.push_back( item( 1, "one" ) );
    vec.push_back( item( 2, "two" ) );

    for ( int i = 0; i < vec.size() ; ++i )
        if ( vec[i].get_i() == 2 ) 
            vec[i].set_s("zwei");
                    
    for ( int i = 0; i < vec.size() ; ++i )
        cout << vec[i].get_i() << " " << vec[i].get_s() << endl;
                    
    return 0;
}

Kurt

I see what you did there. Very nice. But what if "one" and "two" were integers say:

item 1 has 3 as the integer
item 2 has 4 as an interger

I want to find item 2 and add whatever the input file reads to whatever integer item 2 has.

Code:

#include <iostream>
#include <string>
#include <vector>

using namespace std;

class item {

    public:
        item( int id_, int qt_, float pr_ ):id(id_), qt(qt_), pr(pr_) {}
   
        void set_id(int id_)    { id = id_; }
        void set_qt(int qt_)    { qt = qt_; }
        void set_pr(float pr_)  { pr = pr_; }
   
        int get_id()    { return id; }
        int get_qt()    { return qt; }
        float get_pr()  { return pr; }
    private:       
        int id;
        int qt;        
        float pr;        
};


int main() {
    
    vector<item> vec;
    
    vec.push_back( item( 1, 5, 12.5 ) );
    vec.push_back( item( 5, 9, 10.5 ) );
    vec.push_back( item( 4, 8, 4.5 ) );
    vec.push_back( item( 9, 3, 7.7 ) );

    float to_add = 15.33;
    int item_to_change = 4;

    cout << "before changing item " << item_to_change << endl;
    for ( int i = 0; i < vec.size() ; ++i )
        cout << vec[i].get_id() << ": " << vec[i].get_qt() << " " << vec[i].get_pr() << endl;
    
    // search for item with id 'item_to_change'    
    for ( int i = 0; i < vec.size() ; ++i )
        if ( vec[i].get_id() == item_to_change )
            // add 'to_add' to the price 
            vec[i].set_pr( vec[i].get_pr() + to_add );
                    
    cout << "after changing item " << item_to_change << endl;
    for ( int i = 0; i < vec.size() ; ++i )
        cout << vec[i].get_id() << ": " << vec[i].get_qt() << " " << vec[i].get_pr() << endl;
                    
    return 0;
}

Kurt

Originally Posted by ZuK

Code:

#include <iostream>
#include <string>
#include <vector>

using namespace std;

class item {

    public:
        item( int id_, int qt_, float pr_ ):id(id_), qt(qt_), pr(pr_) {}
   
        void set_id(int id_)    { id = id_; }
        void set_qt(int qt_)    { qt = qt_; }
        void set_pr(float pr_)  { pr = pr_; }
   
        int get_id()    { return id; }
        int get_qt()    { return qt; }
        float get_pr()  { return pr; }
    private:       
        int id;
        int qt;        
        float pr;        
};


int main() {
    
    vector<item> vec;
    
    vec.push_back( item( 1, 5, 12.5 ) );
    vec.push_back( item( 5, 9, 10.5 ) );
    vec.push_back( item( 4, 8, 4.5 ) );
    vec.push_back( item( 9, 3, 7.7 ) );

    float to_add = 15.33;
    int item_to_change = 4;

    cout << "before changing item " << item_to_change << endl;
    for ( int i = 0; i < vec.size() ; ++i )
        cout << vec[i].get_id() << ": " << vec[i].get_qt() << " " << vec[i].get_pr() << endl;
    
    // search for item with id 'item_to_change'    
    for ( int i = 0; i < vec.size() ; ++i )
        if ( vec[i].get_id() == item_to_change )
            // add 'to_add' to the price 
            vec[i].set_pr( vec[i].get_pr() + to_add );
                    
    cout << "after changing item " << item_to_change << endl;
    for ( int i = 0; i < vec.size() ; ++i )
        cout << vec[i].get_id() << ": " << vec[i].get_qt() << " " << vec[i].get_pr() << endl;
                    
    return 0;
}

Kurt

That shows almost exactly what I have to do. Except that in that program
float to_add = 15.33;
int item_to_change = 4;

they're declared. I have to read them off the input file which the "to_add" variable is the same as the variable that I read it. I figure I should implement some swapping, but it doesn't look right. This is what I have:

Code:

//this function will change the quantity number of the product
int inventoryItem::getQuantity( string n, int q, double c )
{
	string getQuantity(vector <inventoryItem> &inventoryList, string n);
	string i = 0;

			int q_q = 0;
			void swap (int q_q, int q);
			//swaps the searched quantity into q_q
			int c = q_q;
			q_q = q;
			q = c;

	for ( i = 0; i < inventoryList.size(); i++)
	{
		if (inventoryList[i].getQuantity == n) //searchs for the item number 
 //that the input file has just been read
		{
			
			inventoryList[i].setQuantity( inventoryList[i].getQuantity() + q_q);	
			iventoryList.push_back( n, q, c );	//stores the new quantity along with
							//itemNumber and cost into vector

			cout << n << "\t" << q << "\t" << c <<"\t" << c * q <<endl;
			Output << n << "\t" << q << "\t" << c <<"\t" << c * q <<endl;		
		}
		else
		{
			Error <<"Error: " << n << "not in inventory"<<endl;
		}
	}
	return -1;
}

Sorry, I'm an extreme newbie at C++.