Read String Till Flag (C++) - c++

Question

I'm trying to read a string until a ',' character is reached and store what's been read in a new string.
e.g. "5,6"
// Initialise variables.
string coorPair, xCoor, yCoor
// Ask to enter coordinates.
cout << "Input coordinates: ";
// Store coordinates.
cin >> coorPair
// Break coordinates into x and y variables and convert to integers.
// ?
I also need to store the y value in a separate variable.
What is the best way to do this in C++?
Also, is the best way to validate the input to convert to integers and test the values range?

Answer 1

If you have only one comma seperator in string, you can just find where comma first occurs in input and substring input with found position.
Try following:
std::size_t pos = coorPair.find_first_of(","); //Find position of ','
xCoor = coorPair.substr(0, pos); //Substring x position string
yCoor = coorPair.substr(pos + 1); //Substring y position string
int xCoorInt = std::stoi(xCoor); //Convert x pos string to int
int yCoorInt = std::stoi(yCoor); //Convert y pos string to int

Answer 2

The easiest way to do this is to just let operator>> do all the work for you:
int xCoor, yCoor;
char ch;
cout << "Input coordinates: ";
if (cin >> xCoor >> ch >> yCoor)
{
// use coordinates as needed ...
}
else
{
// bad input...
}

Answer 3

You can do this by specifying you delimiter and parsing the string
std::string delimiter = ",";
size_t pos = 0;
std::string token;
while ((pos = coorPair.find(delimiter)) != std::string::npos) {
token = coorPair.substr(0, pos);
std::cout << token << std::endl;
coorPair.erase(0, pos + delimiter.length());
}
std::cout << coorPair << endl;
The last token example in {5,6} the {6} would be in the coorPair.
Another way would be to use std::getline as pointed in the comments:
std::string token;
while (std::getline(coorPair, token, ','))
{
std::cout << token << std::endl;
}

Answer 4

http://www.cplusplus.com/reference/string/string/getline/
I would recommend using getline().
Below is a small example of how I use it. It takes the input from a stream, so you can either use an ifstream as an input, or do what I did below and convert the string to a stream.
// input data
std::string data("4,5,6,7,8,9");
// convert string "data" to a stream
std::istringstream d(data);
// output string of getline()
std::string val;
std::string x;
std::string y;
bool isX = true;
char delim = ',';
// this will read everything up to delim
while (getline(d, val, delim)) {
if (isX) {
x = val;
}
else {
y = val;
}
// alternate between assigning to X and assigning to Y
isX = !isX;
}