打印功能到输出文件

Question

I am about to be finished with a program I am writing and have reached a roadblock. I am trying to print the contents of a function called print which is called by a pointer.

My problem is I need to print the contents of the function to an output file and am not sure how.

This is my print function:

void English::Print(){

    int formatlength = 38 - (static_cast<int>(firstName.size() + lastName.size()));

    cout << firstName << " " << lastName;
    cout << setw(formatlength) << finalExam;
    cout << setprecision(2) << fixed << setw(11) << FinalGrade();
    cout << setw(4) << Lettergrade() << endl;
}

This is the implementation of the print function:

for (int i = 0; i <= numStudents - 1; i++) {
    if (list[i]->GetSubject() == "English") {
        list[i]->Print();
    }
}

Where the for loop is cycling through my list of Students.

My goal is that the list[i]->Print() will print to my output file.

Answer 1

Simply replace cout with an ostream object, something like :

void English::Print(ostream& fout){
  //ofstream of("myfile.txt", std::ios_base::app);
  int formatlength = 38 - (static_cast<int>(firstName.size() + lastName.size()));

  fout << firstName << " " << lastName;
  fout << setw(formatlength) << finalExam;
  fout << setprecision(2) << fixed << setw(11) << FinalGrade();
  fout << setw(4) << Lettergrade() << endl;
}

Also, you can overload << operator too in your class English

friend ostream& operator <<( ostream& os, const English& E )
{
  //
  return os;
}

And then can simply use:

fout << list[i] ;

Answer 2

Besides the answers above, I think you should try this way, using the C's original file redirection function:

Put this instruction in the first line of your main function:

int main(){
    freopen("out.txt", "w", stdout);
    //your codes

The "out.txt" is the file you wanna to put the data in, "w" means you want to write in the file, and stdout is the standard output stream that has been redirected.