ostream<< overloading for bookinventory program

I am getting an error in my << overloaded function of my book class that I do not understand here is some code snippits:

Code:

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void Book::printAuthors(const vector<Author> & tempauthors){
    vector<Author>::const_iterator constIterator;
   
    for (constIterator=tempauthors.begin();
        constIterator!=tempauthors.end();
        ++constIterator)
        cout << *constIterator<<endl;
}

ostream &operator<<(ostream & os,const Book & tBook){
    os << "\nTitle: "<<tBook.get_title()<<'\n';
    os << "Publisher: "<<tBook.get_publisher()<<'\n';
    os << "Authors: "<<'\n';
    tBook.printAuthors(tBook.authors);
   
    os << endl;
    return os;
}

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the errors:
ook.cpp: In function `std::ostream& operator<<(std::ostream&, const Book&)':
book.cpp:90: passing `const Book' as `this' argument of `void
Book::printAuthors(const std::vector<Author, std::allocator<Author> >&)'
discards qualifiers

You're calling a non-const method on a const object. Change your printAuthors method to:

Code:

---

void Book::printAuthors(const vector<Author> & tempauthors) const {

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thanks for the input that fixed the problem :)