Saving file contents to variables through >> operator - c++

Question

I am trying to read a file and then put the contents (seperator by a space) into variables.
The file's contents are always similar per line. It looks like this:
(50,60) CIRCLE yellow 10
(100,160) CIRCLE red 20
These values are position, name, colour and diameter.
Here is what I've got so far:
#include <SFML/Graphics.hpp>
#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
int main()
{
sf::RenderWindow window(sf::VideoMode(800, 600), "Practicum week 3");
std::ifstream input("input.txt");
std::string name;
std::string line;
sf::Vector2f position;
sf::Color colour;
while (std::getline(input, line))
{
input >> position >> name;
}
while (window.isOpen()) {
sf::Event Event;
while (window.pollEvent(Event)) {
if (Event.type == sf::Event::Closed) { window.close(); }
}
// Start frame
window.clear();
// End frame & display contents
window.display();
}
return 0;
}
The problem here is that at the input >> position >> name; it gives me an error:
"Error: no operator '>>' matches these operands"
operand types are: std::ifstream >> sf::vector2f
I've seen a lot of solutions to this problem being #include missing but as you can see I've already got that covered.
Am I missing something?

Answer 1

The following examples will show you how to take advantage of extraction operator overloading, so that your objects can read values directly from a stream.
You need to overload the operator >> for your object Vector2f. This should look something like this:
istream& operator>>(istream& is, const Vector2f& v2f)
{
is >> v2f.data_member >> v2f.another_data_member;
return is;
}
For example, to read this format: (50,60) CIRCLE yellow 10, your overloaded operator should look like: *slightly in pseudo-code
istream& operator>>(istream& is, const Any_Object& any_obj_instantiation)
{
// input variables
int first_num, second_num;
char open_par, close_par, comma;
Circle circle;
Color color;
int last_num;
// extract ; it skips whitespaces
is >> open_par >> first_num >> comma >> second_num >> cirlce >> color >> last_num;
// failed input
if(!is) return is;
// wrong input format
if(open_par != '(' || close_par != ')' || comma != ','){
is.clear(ios_base::failbit);
return is;
}
// pass the input values to the object
any_obj_instantiation(Vector2f(first_num, second_num), cirlce, color, last_num);
return is;
}
The above code snippet could be used as a benchmark and adapted to the objects you want to populate directly with the input stream operator.

Answer 2

How about stringstream?
#include <iostream>
#include <string>
#include <sstream>
using namespace std;
struct vec{
int x;
int y;
};
int main() {
//string s;
//vec v;
//stringstream ss;
//ss << "20 10 test";
//ss >> v.x >> v.y >> s;
//cout << v.x << " " << v.y << " " << s.c_str(); // 20 10 test
//#EDIT - simple parsing
vec v;
string s = "(2034,10)";
size_t comaPos = s.find_first_of(',');
string x = s.substr(1, comaPos-1);
string y = s.substr(comaPos+1, s.find_first_of(')')-comaPos-1);
v.x = stoi(x);
v.y = stoi(y);
cout << v.x << " " << v.y;
return 0;
}
Note: you can't stream "(20,10)" directly to sf::Vector2f, but you can stream just the coords, as I did above.