Member Function for calculating total

[RabMac]

Hi,

I was wondering if someone could help me with this problem. I need to write a program that takes values from a file and assigns them to an array. It then has to calculate the total of all the values read. I have been told that I need to do this using classes and this is as far as I have got. So far I have managed to read the data from the file and assign it to each object of the class.

However, I am not able to work out how to calculate the total [adding up itsValue from each object] unless I do it outside of the class. Therefore, I was wondering if it is possible to do it within the class and if so how do I do it?

My current reasoning is if I create a private member variable called total and accessor functions, then when I use the accessor functions to set value for total, then I am going to have 10 different totals and not a running total. [there are 10 values in file]

Thanks for any help you can provide.

  #include <iostream>
#include <fstream>
#include <cstdlib>

using namespace std;

class FileData
{
      public:
             void set_size (int size[], int i, short count);
             int get_size () const;
             void set_total ();
             int get_total () const;
             
      private:
              int itsSize, total;
              int number_of_files;
};

const int Max = 100;//sets size of array
int size [Max];//array used to store data from file
FileData FileSize [Max];//creating object

//member function setting value of itsSize using the array which holds the values read from file
void FileData::set_size (int size[], int i, short count)
{
     itsSize = size[i];
     number_of_files = count;
}//end of member function

//member function returns value of itsSize
int FileData::get_size () const
{
    return itsSize;
}//end of member function

//FUNCTIONS
void read_data (short &count, int size []);
//end of functions

int main ()//start of main
{
    short count = 0;//used for controlling element of array and storing value for number of files read
    int i = 0;
    
    read_data (count, size);//function call
    for (i = 0; i < count; i++)
    {
        FileSize [i].set_size(size, i, count);
    }
    for (int j = 0; j < count; j++)
    {
        cout << "Size of file " << j+1 << ": " << FileSize[j].get_size() << endl;
    }
    
    //cout << "Out of loop - Count is: " << count << endl;
    system ("PAUSE");//pauses console for reading display
    return 0;
}//end of main

//function reads data from file and assigns to array. Also calculates number of files read.
void read_data (short &count, int size [])
{
    ifstream myData("i:\\filesize.txt",ios::in); //opening the file for reading.
    if (myData.is_open()) //tests if the file is open
    {
        while (! myData.eof() ) //while the end of file is NOT reached
        {
              myData >> size[count];//reading data from file and assigning to each element of the array
              //cout << "size of file " << count << " is: " << size[count] << endl;
              count++;//counting how many files have been read
        }
        //cout << "Count is: " << count << endl;
        myData.close(); //closing the file
    }
    else cout << "Unable to open file"; //if the file is not open output 
}//end of function 

[Stewbond]

You have an array of FileData objects. The point of the class is that you can store the data into the class and access/manipulate the data with methods.

#include <string>
#include <fstream>
#include <iostream>

class FileData
{
private:
  int m_data[100];
  int m_size;
public:
  FileData() : size(0) // initialize size to 0
  {
  } 
  
  int size() 
  { 
    return m_size; 
  }
  
  void read( string filename )
  {
    ifstream fin( filename , ios::in );
    if (fin.is_open())
    {
      while (! fin.eof() )
        fin >> m_data[ m_size++ ];
      
      fin.close();
    }
    else
    {
      cout << "Unable to open " << filename;
    }
  }
  
  int total()
  {
    int output = 0;
    for (int i = 0; i < m_size; i++)
      output += m_data[i];
    return output;
  }
};

int main()
{
  FileData fd;
  fd.read("i:\\filesize.txt");
  cout << "size: "  << fd.size()  << endl
       << "total: " << fd.total() << endl;
}

[RabMac]

Hi Stewbond,

Not sure if you noticed but I am relatively new to classes and am still trying to get my head around them.

I have had a quick look through your code and can follow most of it. Going to have a mess around and see if I can work it all out.

If there is something I don't get I will be sure to ask for more help. However, I will post back even if it is just to say that I don't need more help.

Thanks very much for the help so far, really appreciate it.

[RabMac]

Hi Stewbond,

Just wanted to thank you again for your help, it was really useful for me. I changed some of the variable names, changed the layout and a couple of minor things, plus added in a couple of new functions and it is working great.

Really appreciate it mate :)