Simple input program crashes - c++

Question

main.cpp:
#include "Login.h"
int main () {
Login();
}
Login.h:
#ifndef LOGIN_H
#define LOGIN_H
#include <string>
#include <iostream>
using namespace std;
class Login
{
public:
Login ();
string getInput () {
return input;
}
void setInput (string x) {
x=input;
}
private:
string input;
};
#endif
Login.cpp:
#include "Login.h"
Login::Login ()
{
Login lo;
lo.setInput("hello");
cout << lo.getInput();
};
I'm just learning to program and I'm trying to make a simple program to display input, but to use a class and object to do it, so I can learn how and ultimately make a program that starts with a login (hence all the "login" names).
When I run this it just crashes, and I have no idea why, or how i would search for a solution to this online, because I don't know even remotely what the problem is.
My question is two-fold:
1. Why is this just crashing?
2. How could I set the parameter in lo.setInput to a user input? (cin)

Answer 1

For 1,
Login::Login()
{
Login lo; // here
You're recursively-calling Login constructor infinitely. When Login lo, the constructor Login::Login is called. it makes its new Login object, and repeat...
Probably you want this:
Login::Login()
{
setInput("hello");
cout << getInput();
}
For 2, just receive input and call with it.
string str;
getline(cin, str);
setInput(str);
In addition, C++ is too hard for newbies to study at first. I recommend you to start with other easier language, such as C, python, etc.

Answer 2

The problem is that your constructor recursively calls itself when it creates within its body local object lo
Login::Login ()
{
Login lo;
lo.setInput("hello");
cout << lo.getInput();
};
Change it the following way
Login::Login ()
{
setInput("hello");
cout << getInput();
};
Though it would be better to define it like (or to allow the compiler to define it itself)
Login::Login () {}
and in main to write
Login lo;
lo.setInput("hello");
cout << lo.getInput();
Also function setInput is invalid
void setInput (string x) {
x=input;
}
There must be
void setInput (string x) {
input = x;
}
The class could be defined like
class Login
{
public:
Login() = default;
Login( const std::string &s ) : input( s ) {}
std::string getInput () const { return input; }
void setInput( const std::string &s ) { input = s; }
private:
std::string input;
};

Answer 3

You may want to create an instance of the Login class and use its methods:
int main(void)
{
Login my_login;
cout << my_login.getInput();
return 0;
}
Another possibility is to create static methods within the Login class. This would essentially be like grouping functions and variables into one package:
class Login
{
public:
static std::string getLoginText(void)
{
std::string text;
cout << "Enter login ID: ";
cin >> text;
return text;
}
};
int main(void)
{
std::string login_text;
login_text = Login::getLoginText();
cout << "Person " << login_text << " is logged in\n";
return 0;
}
Your original main program is confusing as to whether you want to create a temporary instance of the Login class, or call a function called Login. The above techniques make your code more readable by explicitly stating your intentions, rather than relying on unconventional techniques.