Question

I am using the following for easily extracting input and validating the correct type. However, the end of file EOF is not being fired.

template< typename T >
std::istream& read(std::istream &istr, T &val)
{
    std::string s;
    std::getline(istr, s);

    if (istr.good())
    {
        s.erase(s.find_last_not_of(" \n") + 1);

        std::stringstream iss(s);

        iss >> val;

        if (! iss.good())
            istr.setstate(std::ios::failbit);

        char c;
        if (iss.get(c))
            istr.setstate(std::ios::failbit);
    }

    return istr;
}
int main(int argc, char **argv)
{
    int input = 0;

    std::cout << "Please enter an integer>" << std::flush;

    for (;;)
    {
        if (read(std::cin, input))
            break;

        std::cin.clear();
        std::cout << "Please, enter only an INTEGER>" << std::flush;
    }

    std::cout << "Press <enter> to quit>";
    std::cin.ignore(std::numeric_limits< std::streamsize >::max(), '\n');
    return 0;
}

“111” entered does not validate as an integer when it should.

Answer 1

iss >> val reads all the characters and “touches” the end of stream, so it sets off EOF every time.

template< typename T >
std::istream& read(std::istream &istr, T &val)
{
    std::string s;
    std::getline(istr, s);

    if (istr.good()) {
        std::istringstream iss(s); //leave the '\n'

        if (! (iss >> val))
            istr.setstate(std::ios::failbit);

        //if it gets another character that isn't a newline
        char a=0;
        if (iss.get(a) && a!='\n') 
            istr.setstate(std::ios::failbit);
    }

    return istr;
}