Private or Public?

Hi, I have a class of some objects. The class is

Code:

---

#ifndef SALES_DATA_H_INCLUDED
#define SALES_DATA_H_INCLUDED
#include <string>
#include <iostream>
using namespace std;
class Sales_data{
friend ostream &print(ostream&,const Sales_data&);
friend istream &read(istream&,Sales_data&);
public:
    Sales_data &combine(const Sales_data&);
    Sales_data()=default;
    Sales_data(istream &is)
    {
        double price = 0;
        is >> (*this).bookNo >> (*this).units_sold >> price;
        (*this).revenue = price * (*this).units_sold;
    };

    string isbn() const {return bookNo;}
    double avg_price() const {return units_sold?revenue/units_sold:0;}
private:
    std::string bookNo;
    unsigned units_sold;
    double revenue;
};


Sales_data add(const Sales_data &lhs,const Sales_data &rhs)
{
    Sales_data sum=lhs;
    sum.combine(rhs);
    return sum;
}
ostream &print(ostream &os,const Sales_data &item)
{
    os<<item.isbn()<<" was sold "<<item.units_sold<<" copies at total tk "<<item.revenue
    <<" and the average price is "<<item.avg_price()<<endl;
    return os;
}
//input function
istream &read(istream &is, Sales_data &item)
{
double price = 0;
is >> item.bookNo >> item.units_sold >> price;
item.revenue = price * item.units_sold;
return is;
}
Sales_data& Sales_data::combine(const Sales_data &rhs)
{
  units_sold+=rhs.units_sold;
  revenue+=rhs.revenue;
  return *this;
}

#endif // SALES_DATA_H_INCLUDED

---

But, This doesnt compile and gives error at line 27. Says, objects are private with respect to that context. but there is nothing there..

Other than the missing main() this compiles without errors for me.

Jim

Is this a header? Then, don't use "using namespace." It's considered bad practice.
Other than that, you really should be consistent with indentation, remove the "(*this)." parts, and read this: SourceForge.net: Do not remove parameter names - cpwiki

My main source file is

Code:

---

#include <iostream>
#include <string>
using namespace std;
#include "Sales_data.h"
#include "funtions.h"
int main()
{
Sales_data total(cin);
Sales_data sum=total,trans;
while(read(cin,trans))
{


    if(trans.isbn()==total.isbn())
    {
        total.combine(trans);
        sum.combine(trans);

    }
    else
    {
        print(cout,total);
        sum.combine(trans);
        total=trans;
    }
}
print(cout,total);
cout<<"total  "<<sum.units_sold<<" books sold in  "<<sum.revenue<<" dollar"<<endl;
cout<<"average sales price of all book is "<<sum.avg_price()<<" dollar"<<endl;


}

---

and I have also modified the header.. still dont compile

Code:

---

#ifndef SALES_DATA_H_INCLUDED
#define SALES_DATA_H_INCLUDED


class Sales_data{
friend ostream &print(ostream&,const Sales_data&);
friend istream &read(istream&,Sales_data&);
public:
    Sales_data &combine(const Sales_data&);
    Sales_data()=default;
    Sales_data(istream &is)
    {
        double price = 0;
        is >> (*this).bookNo >> (*this).units_sold >> price;
        (*this).revenue = price * (*this).units_sold;
    };

    string isbn() const {return bookNo;}
    double avg_price() const {return units_sold?revenue/units_sold:0;}
private:
    std::string bookNo;
    unsigned units_sold;
    double revenue;
};

Sales_data add(const Sales_data&,const Sales_data&);
ostream &print(ostream&,const Sales_data&);
istream &read(istream&,Sales_data&);

#endif // SALES_DATA_H_INCLUDED

---

and heres the header of my functions

Code:

---

#ifndef FUNTIONS_H_INCLUDED
#define FUNTIONS_H_INCLUDED
Sales_data add(const Sales_data &lhs,const Sales_data &rhs)
{
    Sales_data sum=lhs;
    sum.combine(rhs);
    return sum;
}
ostream &print(ostream &os,const Sales_data &item)
{
    os<<item.isbn()<<" was sold "<<item.units_sold<<" copies at total tk "<<item.revenue
    <<" and the average price is "<<item.avg_price()<<endl;
    return os;
}
//input function
istream &read(istream &is, Sales_data &item)
{
  double price = 0;
  is >> item.bookNo >> item.units_sold >> price;
  item.revenue = price * item.units_sold;
  return is;
}
Sales_data& Sales_data::combine(const Sales_data &rhs)
{
  units_sold+=rhs.units_sold;
  revenue+=rhs.revenue;
  return *this;
}

#endif // FUNTIONS_H_INCLUDED

---

Don't do this:

Code:

---

using namespace std;
#include "Sales_data.h"
#include "funtions.h"

---

using directives should not come before header inclusions like that. Neither should they be at file scope in the header files. Rather, fully qualify those names.

Now, what is the error message(s)?

Found the error, I was Using

Code:

---

cout<<"total  "<<sum.units_sold<<" books sold in  "<<sum.revenue<<" dollar"<<endl;
cout<<"average sales price of all book is "<<sum.avg_price()<<" dollar"<<endl;

---

in main function though it was private.

Quote:

---

using directives should not come before header inclusions like that. Neither should they be at file scope in the header files. Rather, fully qualify those names.

---

Are you suggesting I write the code like this

Code:

---

std::string bookno;
std::cout<<"bla bla";
std::ostream()

---

like this?? but that takes a lot more extra writings..of the same word 'std' whats the problem in using directives?

No, my comments are with respect to your header files at file scope. If you want to have a using directive in a source file after header inclusions, or in a header but within a function scope, go ahead. Just note that indiscriminate use of using directives and using declarations can lead to name collision, possibly causing a compile error or perhaps changing the meaning of your code to something that you did not expect.

Thanks for the advise.. I will be carefull next time..