Reading duplicated objects on files C++ - c++

Question

I'm having some trouble with creating a file system to my program in C++. Well, I am creating a new student, and, if he is the last object that I'm creating before saving the files and closing the program, it gets duplicated. For example, two objects: Daniel, Paul. It shows just the last one duplicated: Daniel, Paul, Paul - in the file.txt.
Here is some code of mine:
FILE READING:
ifstream file;
file.open("file.txt");
while (1)
{
Student *p = new Student();
if (file.eof() || file.bad() || file.fail())
{
break;
}
getline(file, ALLTHESTRINGVARIABLES);
p->STRINGVARIABLES = ALLTHESTRINGVARIABLES;
file >> ANOTHERVARIABLES;
p->NOTSTRINGVARIABLES = ANOTHERVARIABLES;
students.push_back(p);
}
file.close();
FILE WRITING:
fstream file;
file.open("file.txt", ios::out | ios::trunc);
for(unsigned int i = 0; i < students.size(); i++){
file << students[i]->VARIABLEEXAMPLE << endl;
}
file.close();
Thank you!!

Answer 1

The eof(), bad(), fail() will only return true after a try to read some bytes from the file without success. So, put the if verification after the getline().
And just make the new instance of the Student after this if to avoid a memory leak.
Like that:
while (1)
{
getline(file, ALLTHESTRINGVARIABLES);
if (file.eof() || file.bad() || file.fail())
break;
Student *p = new Student();
p->STRINGVARIABLES = ALLTHESTRINGVARIABLES;
file >> ANOTHERVARIABLES;
p->NOTSTRINGVARIABLES = ANOTHERVARIABLES;
students.push_back(p);
}

Answer 2

eof() will not return true until you've actually tried to read beyond the end of the file which is why you see the last line duplicated. The getline will fail and ALLTHESTRINGVARIABLES will contain the values from the latest successful read. You should instead check if the extraction actually succeeded before storing a new Student.
Since you mix unformatted and formatted input, you should also remove the newline (or whatever character you use to separate the records) from the stream.
Change the loop to:
if (std::ifstream file("file.txt"); file)
{
while (std::getline(file, ALLTHESTRINGVARIABLES) >> ANOTHERVARIABLES)
{
// remove the newline or whatever whitespace char you use as record separator
file.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
Student *p = new Student;
p->STRINGVARIABLES = ALLTHESTRINGVARIABLES;
p->NOTSTRINGVARIABLES = ANOTHERVARIABLES;
students.push_back(p);
}
}
I also suggest that you don't store pointers (unless you use dynamic dispatch) but instead store the actual Student objects in a std::vector<Student>. If dynamic dispatch is used, then store std::unique_ptr<Student> in the vector.