Read from the file from different functions - c++

Question

I'm trying to read from the same file from another function but it doesn't work.
I guess the problem is that I'm trying to read from ifstream &input but I don't know the other way to implement that
#include <iostream>
#include <fstream>
using namespace std;
class Student{
public:
char name[40]; // i cant use string
int age;
void Input(ifstream &input)
{
input.getline(name, 40);
input >> age;
}
};
void Read(Student *students, int &numberOfStudents)
{
ifstream input("test.txt");
input >> numberOfStudents;
students = new Student[numberOfStudents];
for (int i = 0; i < numberOfStudents; ++i)
students[i].Input(input);
input.close();
}
int main()
{
int size = 0;
Student *students = NULL;
Read(students, size);
for (int i = 0; i < size; ++i)
cout << students[i].name << endl << students[i].age << endl;
return 0;
}
I made my input file
3
1
2
3
4
5
6
(if the program was working correctly i should've get 1 - name age - 2 etc)
but what i got is no names with ages = 1 2 3 respectively

Answer 1

The program does not work because you define:
void Read(Student *students, int &numberOfStudents)
And then
int size = 0;
Student *students = NULL;
Read(students, size);
The students pointer is passed-by value so Read() can not change the memory address outside the function.
To fix this simply pass the the pointer by-reference:
void Read(Student *& students, int &numberOfStudents)
Lastly as I commented you need to account white space e.g. '\n' line ending
In the file when using >> operator to extract data:
void Input(ifstream &input)
{
input.getline(name, 40);
input >> age;
input.ignore(1);
}
Same for reading the number of students in the file.