input validation for numeric input

Question

I\'m very new to this C++ world and trying write a input validation function for numeric password. This is what I got so far:

#include 
#incl         


        

Answer 1

If there is a failure to convert then the stream itself evaluates to false so you can do this:

int get_int() {
    int i;
    std::cout << "Please enter a number: " << std::endl;
    while(!(std::cin >> i)) {
        std::cin.clear();   //clear flags
        //discard bad input
        std::cin.ignore(std::numeric_limits<std::streamsize>::max()); 
        std::cout << "Incorrect, must be numeric: " << std::endl;
    }
    return i;
 }

Answer 2

This looks like line oriented input. In which case, the usual solution is to use getline:

bool parseNumber( std::string const& text, int& results )
{
    std::istringstream parser( text );
    return parser >> results >> std::ws && parser.peek() == EOF;
}

int getNumber()
{
    int results;
    std::string line;
    while ( ! std::getline( std::cin, line ) || ! parseNumber( line, results ) ) 
    {
        std::cin.clear();
        std::cout << "Only 'numeric' value(s) allowed:";
    }
    return results;
}