usage of istream in class constructor c++ -

i have text file contains list of students , marks , looks this:

name_of_student 78 4; 98 5; 90 5; 63 3; ... 

i have assignment create class read , store data. i've done far.

group.h class subject { public:     subject(int mark0, int mark1);     subject();     int get_m0() { return mark0; }     int get_m1() { return mark1; } private:     int mark0;     int mark1; };  class student { public:     student(string name);     student();     vector<subject>my_marks;     string get_name() { return name; } private:     string name; };  class reading { public:     reading(vector<student>, istream& );     istream& read_student(); private:     vector<student>group;     istream& is; };  text.cpp subject::subject(int m0, int m1) : mark0(m0), mark1(m1) {}  subject::subject() : mark0(1), mark1(1) {}  student::student(string n0) : name(n0) {}  student::student() : name("null") {}  reading::reading(vector<student>group0, istream& is0) : group(group0), is(is0) {}  istream& reading::read_student() {     string n;     >> n;     if (!is) return is;     student st = student(n);     (int = 0; < 4; ++i)     {         int m0, m1;         >> m0 >> m1;         char ch;         >> ch;         subject sub = subject(m0, m1);         st.my_marks.push_back(sub);     }     group.push_back(st);     return is; } 

it compiles, refuses read anything.

int main() {    ifstream ifs("text");    if(!ifs) error("can`t open input file");    vector<student> group;    readding r(group, ifs);    r.read_student();    cout << group.size(); } 

and shows:

0 

if has ideas i'd appreciate it.

in reading::read_student(), filling member variable reading::group. not filling function variable group in main.

use:

int main() {    ifstream ifs("text");    vector<student> group;    readding r(group, ifs);    r.read_student();    cout << r.group.size();    //     ^^^^^^^^ access member variable of r. } 

if want function variable group filled up, reading needs store reference input group.

class reading { public:     reading(vector<student> & , istream& );     //          ^^^^^^ take reference input     istream& read_student(); private:     vector<student>& group;     //          ^^^^^^ store reference     istream& is; };