Reading file to class object

Question

I am having trouble reading a file to my class object's members. It says it cannot read the file.

This is my class:

const int SIZE_OF = 5;

class Student
{
public:
    Student();
    Student(const Student &);
    Student(string, int, int, int, int, int);
    friend std::istream& operator >> (std::istream& in, Student& S);
    void display();
private:
    string lastName;
    int grades[SIZE_OF];
};

The cpp file associated with my class object to define the functions:

#include "Student.h"

Student::Student()
{
    int i;
    string lastName = "default";
    for (i = 0; i < 5; i++)
    {
        grades[i] = 0;
    }

}

Student::Student(const Student & S)
{
    int i;
    lastName = S.lastName;
    for (i = 0; i < 5; i++)
    {
        grades[i] = S.grades[i];
    }
}

Student::Student(string S, int a, int b, int c, int d, int e)
{
    lastName = S;
    grades[0] = a;
    grades[1] = b;
    grades[2] = c;
    grades[3] = d;
    grades[4] = e;
}

std::istream& operator >> (std::istream& in, Student& S)
{
    char dummy;
    in >> S.lastName >> S.grades[0]
        >> dummy >> S.grades[1]
        >> dummy >> S.grades[2]
        >> dummy >> S.grades[3]
        >> dummy >> S.grades[4];
    return in;

}

void Student::display()
{
    int i;
    int sum = 0;
    double average;
    cout << "Last Name: " << lastName << endl;
    cout << "Grades: " << endl;
    for (i = 0; i < 5; i++)
    {
        cout << grades[i] << endl;
    }
    for (i = 0; i < 5; i++)
    {
        sum = sum + grades[i];
    }
    average = sum / 5;
    cout << "Average: " << average;

}

And finally, the main function that I have so far to test the file opening and reading it to the various variables inside the class.

void main()
{
    fstream     File;
    string      FileName = "ProgramSixData.txt";
    bool        FoundFile;
    string      Line;
    Student     testStudent;

    do {
        File.open(FileName, ios_base::in | ios_base::out);
        FoundFile = File.is_open();
        if (!FoundFile)
        {
            cout << "Could not open file named " << FileName << endl;
            File.open(FileName, ios_base::out); // try to create it
            FoundFile = File.is_open();
            if (!FoundFile)
            {
                cout << "Could not create file named " << FileName << endl;
                exit(0);
            }
            else;
        }
        else;
    } while (!FoundFile);
    do {
        File >> testStudent;
        if (File.fail())
        {
            cout << "Read Failed" << endl;
            cout << "Bye" << endl;
            exit(0);
        }
        else;
        testStudent.display();
    } while (!File.eof());
    cout << "Bye" << endl;
    File.close();
}

The text document that I am reading from is the following:

George
75,85,95,100,44
Peter
100,100,100,100,100
Frank
44,55,66,77,88
Alfred
99,88,77,66,55

How do I save each of the names and the associated 5 grades to a particular object of the student class?

Answer 1

You are digging too deep. I made an example solution for you, focusing on the parsing. Things could be way shorter and we could instantly make the students instead of doing it the map way, but I want you to understand how to parse the file, because that is obviously what you are struggling with. Ask me anything about the code if you don't understand it.

void main()
{
    string      FileName = "ProgramSixData.txt";
    bool        FoundFile;
    string      Line;
    vector<Student> Students;

    ifstream file(FileName); //an ifstream is an INPUTstream (same as a fstream with ::in flag. Passing the FileName as argument opens that file
    if (file.fail()) //check if the file opened correctly
    {
        cout << "Failed to open inputfile\n";
        return;
    }

    map <string, vector<int>> studentAndGrades; //map is a container that uses keys and values, every key has a value, we will use the name of the student as the key to access his marks (a vector of int)
    vector<string> allLines;
    string line;
    while (file >> line) //these 2 linessimply reads ALL the lines to the allLines vector
        allLines.push_back(line);

    for (size_t i = 0; i < allLines.size(); i += 2) //loop over all lines, by 2 at a time (1 for the students name and 1 for his marks)
    {
        vector<int> numbers;

        size_t lastCommaIdx = 0;
        size_t currentCount = 0;
        string scores(allLines[i + 1]); //make a copy of allLines[i + 1] for convenient use
        bool firstLine = true;
        for (size_t i = 0; i < scores.size(); ++i) //following code is just to split the numbers from the comma's and put them in a vector of int
        {
            if (scores[i] == ',')
            {
                if (firstLine)
                {
                    numbers.push_back(stoi(scores.substr(lastCommaIdx, currentCount)));
                    firstLine = false;
                }
                else
                {
                    numbers.push_back(stoi(scores.substr(lastCommaIdx + 1, currentCount)));
                }
                lastCommaIdx = i;
                currentCount = 0;
            }
            else
            {
                ++currentCount;
            }
        }
        numbers.push_back(stoi(scores.substr(lastCommaIdx + 1))); //last number
        studentAndGrades.insert(make_pair(allLines[i], numbers)); //finally, insert them in the map
    }

    for (const auto& student : studentAndGrades)
        Students.push_back(Student(student.first, student.second[0], student.second[1], student.second[2], student.second[3], student.second[4])); //make students from the information that we read into the map

    for (auto& student : Students) //display all students with a range based for loop
        student.display();
    file.close();
}