Why does reading a record struct fields from std::istream fail, and how can I fix it?

Question

Suppose we have the following situation:

• A record struct is declared as follows

---

struct Person {
    unsigned int id;
    std::st         


        

Answer 1

Here's an implementation of a manipulator I came up with that counts the delimiter through each extracted character. Using the number of delimiters you specify, it will extract words from the input stream. Here's a working demo.

template
struct word_inserter_impl {
    word_inserter_impl(std::size_t words, std::basic_string& str, charT delim)
        : str_(str)
        , delim_(delim)
        , words_(words)
    { }

    friend std::basic_istream&
    operator>>(std::basic_istream& is, const word_inserter_impl& wi) {
        typename std::basic_istream::sentry ok(is);

        if (ok) {
            std::istreambuf_iterator it(is), end;
            std::back_insert_iterator dest(wi.str_);

            while (it != end && wi.words_) {
                if (*it == wi.delim_ && --wi.words_ == 0) {
                    break;
                }
                dest++ = *it++;
            }
        }
        return is;
    }
private:
    std::basic_string& str_;
    charT delim_;
    mutable std::size_t words_;
};

template
word_inserter_impl word_inserter(std::size_t words, std::basic_string& str, charT delim = charT(' ')) {
    return word_inserter_impl(words, str, delim);
}

Now you can just do:

while (ifs >> actRecord.id >> word_inserter(2, actRecord.name) >> actRecord.age) {
    std::cout << actRecord.id << " " << actRecord.name << " " << actRecord.age << '\n';
}

Live Demo