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

Another solution is to require certain delimiter characters for a particular field, and provide a special extraction manipulator for this purpose.

Let's suppose we define the delimiter character ", and the input should look like this:

1267867 "John Smith"      32   
67545   "Jane Doe"        36  
8677453 "Gwyneth Miller"  56  
75543   "J. Ross Unusual" 23  

Generally needed includes:

#include 
#include 
#include 

The record declaration:

struct Person {
    unsigned int id;
    std::string name;
    uint8_t age;
    // ...
};

Declaration/definition of a proxy class (struct) that supports being used with the std::istream& operator>>(std::istream&, const delim_field_extractor_proxy&) global operator overload:

struct delim_field_extractor_proxy { 
    delim_field_extractor_proxy
       ( std::string& field_ref
       , char delim = '"'
       ) 
    : field_ref_(field_ref), delim_(delim) {}

    friend 
    std::istream& operator>>
       ( std::istream& is
       , const delim_field_extractor_proxy& extractor_proxy);

    void extract_value(std::istream& is) const {
        field_ref_.clear();
        char input;
        bool addChars = false;
        while(is) {
            is.get(input);
            if(is.eof()) {
                break;
            }
            if(input == delim_) {
                addChars = !addChars;
                if(!addChars) {
                    break;
                }
                else {
                    continue;
                }
            }
            if(addChars) {
                field_ref_ += input;
            }
        }
        // consume whitespaces
        while(std::isspace(is.peek())) {
            is.get();
        }
    }
    std::string& field_ref_;
    char delim_;
};

---

std::istream& operator>>
    ( std::istream& is
    , const delim_field_extractor_proxy& extractor_proxy) {
    extractor_proxy.extract_value(is);
    return is;
}

Plumbing everything connected together and instantiating the delim_field_extractor_proxy:

int main() {
    std::istream& ifs = std::cin; // Open file alternatively
    std::vector persons;

    Person actRecord;
    int act_age;
    while(ifs >> actRecord.id 
              >> delim_field_extractor_proxy(actRecord.name,'"')
              >> act_age) {
        actRecord.age = uint8_t(act_age);
        persons.push_back(actRecord);
    }

    for(auto it = persons.begin();
        it != persons.end();
        ++it) {
        std::cout << it->id << ", " 
                      << it->name << ", " 
                      << int(it->age) << std::endl;
    }
    return 0;
}

See the working example here.

NOTE:
This solution also works well specifying a TAB character (\t) as delimiter, which is useful parsing standard .csv formats.