How do you make a vector of class objects?

Question

I'm a bit confused as to how vectors work. What I'm trying to do is create a vector of 5 TaxBill objects. Then, what I want to do is read from an input file that has the names and different tax rates for 5 states. I want to store the name of the state in the object and the tax rates of the state in an array in int main() .

Here's the input file called "Tax Rates.dat". The numbers are the sales, property and income tax rate, respectively, for each state.

TEXAS      .0825 .02 -.03
MARYLAND   .065 .04 .05
OHIO       .03 .025 .03
CALIFORNIA .095 .055 .045
MAINE      .02 .015 .02

Here's my class interface called "Tax Bill.h".

using namespace std;

class TaxBill
{
public:
      void setValue(string, int);
      void dataValid(double&, double&, double&);

private:
      string Name;
      int index;
      double taxBill;
}

Here's my class implementation called "Tax Bill.cpp".

#include "Tax Bill.h"

void TaxBill::setValue(string name, int x)
{}


void TaxBill::dataValid(double& a, double& b, double& c)
{
      if(a < 0)
            a = 0;
      if(b < 0)
            b = 0;
      if(c < 0)
            c = 0;

      return;
}

Here's my main source code so far.

#include <iostream>
#include <string>
#include <iomanip>
#include <fstream>
#include <vector>
#include "Tax Bill.h"

using namespace std;


int main()
{
      const int SALARY = 100000,
            HOUSE = 246000,
            PURCHASE = 36000;
      ifstream fin;
      fin.open("Tax Rates.dat");
      vector <TaxBill> someVector (5);
      double sales,
            property,
            income;
      double taxRates[5][3];
      string name;

      if(!fin)
            return 0;
      else
      {
            for(int i = 0; fin >> name >> sales >> property >> income; i++)
            {
                  dataValid(sales, property, income);
                  taxRates[i][0] = sales;
                  taxRates[i][1] = property;
                  taxRates[i][2] = income;
            }
      }

The for loop is where I want to store the name of the state read from the input file and i into the string Name and index of the class object. The reason for the index is because later in the program I want to sort the objects in the vector alphabetically but not the array where the corresponding tax rates are stored.

I also don't want to use the function push_back() .

I guess my question is, how do I make an vector of 5 class objects and access them?

Please keep in mind that my program is hardly complete and it's this one hurdle that's holding me back.

Answer 1

Here example of using vector from your code. Here you declare

vector <TaxBill> someVector (5);

So now, you have someVector[0] - [4] (5 in total). To use it, actually you just have to assign it like an normal array.

someVector[0].{insert property here}

But wait, in your class, there is no clear way to set the string Name and Index. So i think you forget to place it here, hence i make my own in the class.

class TaxBill
{
public:
      void setValue(string Name, int Index){
         name = Name; index = Index;
      }
      void dataValid(double&, double&, double&);

private:
      string name;
      int index;
      double taxBill;
}

Now to use the vector, i just used the property this way

someVector[0].setValue("someName",1);

Tada, you get it to works. Btw, i dont know why you declare a procedure in the class, but you want to used it multiple times in main program. I mean this one

dataValid(sales, property, income);

to used it, i suggest you make a procedure in main program rather than in class and anyway that line should produce an error anyway. :)