std :: string >> std :: string没有运算符“ >>”

Question

I'm having a problem and I'm not sure how to fix it.

Here is a search function that I made from which I'm receiving the error;

void guestSearch()
{
    &Reservation::getfirstName;
    &Reservation::getlastName;

    &Date::getday;
    &Date::getmonth;
    &Date::getyear;
    Hotelreservation reg;
    reg.duration;
    reg.occupants;
    &Contact::getareaCode;
    &Contact::getexchange;
    &Contact::getline;

    system("cls");
    cout<<"Enter Line Number for the Guest you are searching for:";
    cin>>line;
    string line2= to_string(line);
    line2.append(".txt");

    ifstream filemain(line2);
    while(firstName>>lastName>>day>>month>>year>>duration>>occupants>>areaCode>>exchange>>line)
    {
        int firstNameLength=firstName.size();
        int lastNameLength=lastName.size();
        int lengthTotal=firstName+lastName;

        string result;
        cout<< "Is this the correct Guest (y/n)"<<endl;
        cout<<"Name"<<firstName<<" "<<lastName<<end;
        cin>>result;

        if(result=="y")
        {
            system("cls");
            cout<<"Name";
            for(int y = 1; y<lengthTotal; y++)
            {
                cout<< " ";
            }
            cout<<"Reservation Date";
            for(int z=1; z<2; z++)
            {
                cout<< " ";
            }
            cout<<"Duration of Stay";
            for(int x=1; x<2; x++)
            {
                cout<< " ";
            }
            cout<<"Occupants";
            for(int u=1; u<2; u++)
            {
                cout<< " ";
            }
            cout<<"Contact Number";
            for(int v=1; v<2; v++)
            {
                cout<< " ";
            }
        }
        cout<<"Date Reservation was made:"<<day<<"/"<<month<<"/"<<year<<endl;
        cout<<"Duration Of Stay:"<<duration<<endl;
        cout<<"Occupants:"<<occupants<<endl;
        cout<<"Contact Number:"<<areaCode<<"-"<<exchange<<"-"<<line<<endl;
    }
}

I'm receiving an error at the while declaration after firstName ">>" , I get this:

IntelliSense: no operator ">>" matches these operands operand types are: std::string>>std::string"

Answer 1

You misunderstand the concept, though it is possible to chain multiple std::string instances trhough operator >> , first object should be of type inherited from std::istream such as ifstream fileman in your case:

while( fileman >> firstName >> lastName >> ... )

it works because you can treat that expression as:

while( fileman.operator>>( firstName ).operator>>( lastName ) ... )

and because std::istream::operator>> returns reference to std::istream again that chain invocation works.

There is no such operator in std::string