调用函数，只返回0

Question

Alrighty, the goal of what I am trying to do right now is call the function getSingleStudentInfo, which contains the student's number, last name, and age. In the end this program is designed to do two things, the first being the single student info, the second, printing out an array of 20 students. Disregard the second part, as I have not really gotten into that part yet, so ignore anything involving vectors.

The problem that I am having is that in main the first thing that the program will do is ask you to press 1 for the single info or 2 for the full 20 peoples info. The program compiles fine, but what happens is, no matter what number you enter, the program will say "process returned 0 (0x0)" and be done, I'm having a hard time figuring out why it is doing that instead of printing out the single students info, being "student's ID number is 400" "student's last name is: Simmons" "student's age is: 20"

#include <iostream>
#include <vector>
#include <string>
using namespace std;

struct Student {
    int studentNumber = 400;
    string lastName = "Simmons";
    int age = 20;
};

Student s;
int selection;
vector<int> studentNumber (20);
vector<string> lastName;
vector<int> age (20);

void getSingleStudentInfo (int studentNumber, string lastName, int age) {
    cout << "Student's ID number is: ";
    cout << s.studentNumber << endl;
    cout << "Student's last name is: ";
    cout << s.lastName << endl;
    cout << "Student's age is: ";
    cout << s.age << endl;
return;
};

int main()
{
    cout << "Press '1' to see a single student data entry" << endl;
    cout << "Press '2' to see all 20 student records" << endl;
    cin >> selection;
    if (selection == 1) {
    getSingleStudentInfo;
    };
    /*for (vector<int>::size_type i = 0; i <= 20; i++)
    {
        cout << "Student's ID number is: " << 400 + i << endl;
    }
    return 0;*/
}

Answer 1

You need to call the function, eg

if (selection == 1)
{
    getSingleStudentInfo(7, "Johnson", 20);
}

However, it seems like by the implementation, this should be a method off of the student itself

struct Student {
    int studentNumber = 400;
    string lastName = "Simmons";
    int age = 20;
    void getSingleStudentInfo() const;
};

Then you'd call it off a Student instance

Student s{400, "Simmons", 20};
s.getSingleStudentInfo();

Then if you had a vector of Student you could do

std::vector<Student> students; // assume this has been populated
std::for_each(begin(students),
              end(students),
              [](const Student& s){s.getSingleStudentInfo();});

To print in columns, you could change your function to something like

void Student::getSingleStudentInfo()
{
    cout << s.studentNumber << '\t'
         << s.lastName << '\t'
         << s.age << endl;
};