Manipulating vectors inside class methods - c++

Question

I just started learning about vectors, and they seem really handy, if talking about lists from a file. But I'm having a problem while trying to return a new vector from a class method and put it to another method of the same class.
i.e.
#include <iostream>
#include <vector>
#include <fstream>
#include <string>
using namespace std;
class A
{
public:
string name;
string age;
};
class Test
{
string name;
string age;
public:
void get(vector<A> students)
{
vector<A> specificStudents;
//rewrite a couple of students from vector<A>students
//to vector<A> specificStudents
};
void set(vector<A> specificStudents)
{
//I need to get vector<A> specificStudents here
};
};
int main()
{
vector<A> students;
A stud;
ifstream file("file.txt");
for (int i = 0; i < file.eof(); i++)
{
getline(file, stud.name);
getline(file, stud.age);
students.push_back(stud);
};
Test test;
test.get(students);
return 0;
}
Can I return it as a function argument?

Answer 1

It is not entirely clear, but do you want to save a copy of students inside test?:
class Test
{
vector<A> specificStudents;
public:
const vector<A>& get() const
{
return specificStudents;
}
void set(const vector<A>& students)
{
specificStudents = students;
// maybe modify `specificStudents` here in some way or assign it differently
}
};
int main()
{
vector<A> students;
A stud;
ifstream file("file.txt");
while (getline(file, stud.name) && getline(file, stud.age))
{
students.push_back(stud);
}
Test test;
test.set(students);
//... Do something with test
return 0;
}
If you don't know yet what & and const mean in this, you can just remove them (until you learn about them).
You seem to have gotten get and set mixed up. By usual convention, get gets something stored in the class object to the caller and set sets something in the class object (with a value provided by the caller).
I also fixed your input loop. I don't know what you thought file.eof() does, but comparing to i does not do anything useful.
Also be aware of where ; belongs and where it doesn't. It belongs after single statements and class definitions, but not after } of function definitions or other statement blocks, such as the one of while.

Answer 2

YES, you can return vector from a function.
To do this you can write a function like this one:
std::vector<A> get(vector<A> students)
and the inside it return the vector. An example can be:
vector<A> get(vector<A> students)
{
vector<A> specificStudents;
//rewrite a couple of students from vector<A>students
//to vector<A> specificStudents
return specificStudents;
};