file IO only writing for 1 element

I have a vector of students and im trying to write them into a txt file. However, it will only write 1 student only. I also am not really sure on how to implement read file also. I got something in my mind but I;m not sure if it's correct or not.

calling write to file function from main

Code:

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for(vector<clsStudent*>::const_iterator it = student.begin(); it != student.end();++it)
{
    (*it)->writeToFile();
}

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Code:

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const char * filename = "studentinfo.txt";


void clsLocalStudent::writeToFile()
{
    clsUniversityProgram *ptrProgram;
    ptrProgram = getProgram();


  ofstream out(filename);
  if(out)
  {
      out << getName() << "\t"
            << getDateOfBirth() << "\t"
            << getGender() << "\t"
            << getNationality() << "\t"
            << getGPA() << "\t"
            << ptrProgram->getProgramName() << "\t"
            << ptrProgram->getProgramCode() << "\t"
            << ptrProgram->getProgramFees() << "\t"
            << getAccounts()->getAccountHolderName() << "\t"
            << getAccounts()->getAccountHolderID() << "\t"
            << getAccounts()->getAccountHolderDOB() << "\t"
            << getAccounts()->getAccountStartDate() << "\t"
            << getAccounts()->getPrincipal() << "\t"
            << getAccounts()->getYear() << "\t"
            << getAccounts()->getCI() << "\t"
            << getAccounts()->getC_Amount() << "\t"
            << calculateFees() << "\t"
            << getIC() << "\t"
            << getState();
      out.close();
  }
  else
      cerr << "\nCannot open " << filename << " for writing" << endl;
}

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what i had in mind

Code:

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void readFromFile(vector <clsStudent *> &s)
{
string name, double GPA;
  ifstream in(filename);
  if(in)
  {
      in >> name >> GPA;
      in.close();
  }
  else
      cerr << "\nCannot open " << filename << " for reading" << endl;

  student = new clsLocalStudent(name, GPA); // parameterized constructor
  s.push_back(student);
}

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So the first thing your write to file function does is delete all prior contents of the file. If you don't want that to happen, you should probably tack on ios::append in your constructor there.

EDIT: Apparently I mean app instead of append.

this?

Code:

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ofstream out(filename, ios::app);

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do i need to do anything to make it append at the end of file?

I don't think "if" stands for output file, do you?

Quote:

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Originally Posted by tabstop

I don't think "if" stands for output file, do you?

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Haha, my mistake. Thanks

Decouple the opening of the file with the writing to the file. For example:

Code:

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void clsLocalStudent::writeToFile(std::ostream& out) const
{
    clsUniversityProgram* ptrProgram = getProgram();

    out << getName() << "\t"
        << getDateOfBirth() << "\t"
        << getGender() << "\t"
        << getNationality() << "\t"
        << getGPA() << "\t"
        << ptrProgram->getProgramName() << "\t"
        << ptrProgram->getProgramCode() << "\t"
        << ptrProgram->getProgramFees() << "\t"
        << getAccounts()->getAccountHolderName() << "\t"
        << getAccounts()->getAccountHolderID() << "\t"
        << getAccounts()->getAccountHolderDOB() << "\t"
        << getAccounts()->getAccountStartDate() << "\t"
        << getAccounts()->getPrincipal() << "\t"
        << getAccounts()->getYear() << "\t"
        << getAccounts()->getCI() << "\t"
        << getAccounts()->getC_Amount() << "\t"
        << calculateFees() << "\t"
        << getIC() << "\t"
        << getState();
}

// ...

const char* filename = "studentinfo.txt";
ofstream out(filename);
if (out)
{
    for (vector<clsStudent*>::const_iterator it = student.begin(); it != student.end(); ++it)
    {
        (*it)->writeToFile(out);
    }
}
else
{
    cerr << "\nCannot open " << filename << " for writing" << endl;
}

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In fact, for this purpose, it is common to overload operator<< to do what your writeToFile member function does.