String not getting passed into class function - c++

Question

class Message {
public:
void changeSubject(string);
string getSubject();
private:
string subject;
};
void Message::changeSubject (string subjecto) //change subject{
subject = subjecto;
}
string Message::getSubject () //return subject {
return subject;
}
int main ()
{
Message person;
string aboutwhat;
cout << "Enter subject" << endl;
getline(cin, aboutwhat);
person.changeSubject(aboutwhat);
cout << person.getSubject();
return 0;
}
Above isn't the full code. The problem right now is that it prints "Enter Subject" and ends the program. Why am I not prompted to cin?

Answer 1

Your code as posted has several issues and doesn't compile. The following works for me
// Include al necessary headers:
#include <iostream>
#include <string>
// Either qualify the namespace of `std::string`, `std::cin`, etc
// or place a using statement like follows
using namespace std;
class Message {
public:
void changeSubject(string);
string getSubject();
private:
string subject;
};
void Message::changeSubject (string subjecto) //change subject
{ // <<< You have hidden the opening brace after the comment above
subject = subjecto;
}
string Message::getSubject () //return subject
{ // <<< You have hidden the opening brace after the comment above
return subject;
}
int main ()
{
Message person;
string aboutwhat;
cout << "Enter subject" << endl;
getline(cin, aboutwhat);
person.changeSubject(aboutwhat);
cout << person.getSubject();
return 0;
}
See the working sample here please.
Since you have stated in your question, "This isn't the full code", I'd suspect you have some error in the other parts that weren't shown.
"Why am I not prompted to cin?"
One likely possibility is you have had other inputs on cin before, that were invalid and cin got into fail() state.
To prevent this, you can put a cin.clear(); statement before the getline() call.
If you take inputs like e.g. numbers, you should check for validity like this
int x;
do {
cout << "Enter a number please: "
if(cin >> x) {
break;
}
cout << "Not a valid number, try again." << endl;
cin.clear();
} while(true);

Answer 2

Since your code above looks correct.
I would suggest you first get the prompting working first.
Then add back more code later.
I just tested the following in my own environment
#include <iostream>
#include <string>
main ()
{
std::string aboutwhat;
std::cout << "Enter subject" << std::endl;
std::getline (std::cin,aboutwhat);
std::cout << "Subject: " << aboutwhat << std::endl;
return 0;
}