C++ Populating a vector of objects with user input - c++

Question

I am new to vectors and new to classes.That being said, I have found some posts about how to create a vector of objects. I want to know how would one go about creating a vector of objects from user input? Say the program asks the user to give the number of employees(class) he/she wants to create. The user wants to add 5 employees. So user must input the employee's last name and first name. I have a for loop in mind but I am not sure how to go about grabbing the user input (Maybe using getline and push_back?) and storing it in the vector.
//Lets say class.h looks like this
class Employee
{
private:
string lastName;
string firstName;
public:
void setLastname(string);
void setFirstname(string);
string getLastname() const;
string getFirstname() const;
}

Answer 1

Your Employee class should have a constructor. When gathering input, you need all the constructor arguments. Then, to add an Employee to a vector<Employee>, call employees.emplace_back( ctor-arguments ).

Answer 2

std::vector has a nice method called emplace_back, which
Appends a new element to the end of the container. The element is constructed through std::allocator_traits::construct, which typically uses placement-new to construct the element in-place at the location provided by the container.
So the only thing you are missing to be able to use it is an appropriate constructor.
#include <iostream>
#include <string>
#include <vector>
using namespace std;
class Employee
{
private:
string firstName;
string lastName;
public:
void setLastname(string);
void setFirstname(string);
string getLastname() const{return lastName;}
string getFirstname() const{return firstName;}
//create a constructor
Employee(string firstName, string lastName)
: firstName(firstName), lastName(lastName)
{}
};
int main()
{
vector<Employee> emp;
int count = 0;
cout << "Enter the amount of employees to add:" << endl;
cin >> count;
string firstName, lastName;
for(int i = 0; i < count; ++i)
{
cout << "Please enter the first and last names" << endl;
cin >> firstName;
cin >> lastName;
emp.emplace_back(firstName, lastName);
}
for(const Employee & e : emp)
{
cout << "Employee:" << endl;
cout << e.getFirstname() << " " << e.getLastname() << endl;
}
}

Answer 3

Other users have provided a good examples explaining how to use emplace_back in modern C++.
If you work with pre-C++11 versions, there is no emplace_back method. In this case, you can collect data in your vector manually using old-style push_back. You can simply define a vector:
vector<Employee> employees;
Then, you can read your data line by line, create new objects, fill them according to your business logics and append to your vector:
int n;
int main()
{
cout << "Enter number of employyes: "; cin >> n;
for (int i = 0; i < n; i++)
{
std::string s;
Employee employee; // Create object
cout << "Employee " << i << ". First name: "; cin >> s;
employee.setFirstname(s); // Fill object
cout << "Employee " << i << ". Last name: "; cin >> s;
employee.setLastname(s); // Keep filling it
cout << "Welcome, " << employee.getFirstname() << " " << employee.getLastname() << endl;
employees.push_back(employee); // Add to vector
}
}
You can also define a constructor taking both firstname and lastname as arguments to make it easier to work with.

Answer 4

class Employee
{
private:
string lastName;
string firstName;
public:
Employee(string paramLastName, string paramFirstName) : lastName(move(paramLastName)), firstName(move(paramFirstName)) {}
void setLastname(string);
void setFirstname(string);
string getLastname() const;
string getFirstname() const;
}
You need a constructor that takes two strings as input. Obviously you could do without this but this reduces verbosity.
Employee(string paramLastName, string paramFirstName) :
lastName(move(paramLastName)), firstName(move(paramFirstName)) {}
You will need to call it in this way.
vector<Employee> inp;
string tmp1, tmp2;
while(std::cin>>tmp1 >> tmp2) {
inp.emplace_back(tmp1, tmp2);
}
(This is assuming that you will compile with c++11 support)