Question

I have the following data in a c++ string

John Doe 01.01.1970

I need to extract the date and time from it into int variables. I tried it like this:

int last_space = text_string.find_last_of(' ');
int day = int(text_string.substr(last_space + 1, 2));

But I got invalid cast from type ‘std::basic_string’ to type ‘int’. When I extract the “John Doe” part in another string variable, all works fine. What’s wrong?

I am trying to compile it with g++ -Wall -Werror.

Answer 1

Use streams to decode integers from a string:

#include <iostream>
#include <sstream>
#include <string>

int main()
{
    std::string         x = "John Doe 02.01.1970";

    std::string         fname;
    std::string         lname;
    int                 day;
    int                 month;
    int                 year;
    char                sep;

    std::stringstream   data(x);
    data >> fname >> lname >> day >> sep >> month >> sep >> year;

    std::cout << "Day(" << day << ") Month(" << month << ") Year(" << year << ")\n";
}

The operator >> when used with a string variable will read a single (white) space separate word. When used with an integer variable will read an integer from the stream (discarding any proceeding (white) space).