cpp operator = aka assignment operator overload

//model/book.cpp
void book::operator=(const book &bk){
    std::cout<<std::endl<<std::endl<<std::endl<<"Called operator assignment overloaded!"
    <<std::endl<<std::endl<<std::endl;
    this->set_idx(bk.get_idx());
    this->set_id(bk.get_id());
    this->set_abstract(bk.get_abstract());
    this->set_author(bk.get_author());
    this->set_comment(bk.get_comment());
    this->set_content(bk.get_content());
    this->set_header(bk.get_header());
    this->set_isbn(bk.get_isbn());
    this->set_summary(bk.get_summary());
    this->set_title(bk.get_title());
    this->set_topic(bk.get_topic());
}

void book::print_book(const book&bk){
    std::cout<<std::fixed<<bk.get_idx()<<","<<bk.get_id()<<","<<bk.get_abstract()<<","<<bk.get_author()
    <<","<<bk.get_comment()<<","<<bk.get_content()<<","<<bk.get_header()<<","<<bk.get_isbn()<<","
    <<bk.get_summary()<<","<<bk.get_title()<<","<<bk.get_topic()<<std::endl;
}

//util.cpp
#include "util.h"

std::string util::get_time_now()
{
    std::chrono::high_resolution_clock::time_point now = std::chrono::high_resolution_clock::now();
    time_t raw_time = std::chrono::high_resolution_clock::to_time_t(now);
    struct tm tm_info = *std::localtime(&raw_time);
    std::chrono::milliseconds mills = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch());
    std::chrono::seconds seconds = std::chrono::duration_cast<std::chrono::seconds>(now.time_since_epoch());
    uint64_t mills_count = mills.count() - seconds.count() * 1000;
    std::stringstream ss;
    ss << std::put_time(&tm_info, "%Y%m%d%H%M%S") << std::setfill('0') << std::setw(3) << mills_count;
    return ss.str();
}

std::string util::get_uuid()
{
    uuid_t new_uuid;
    char *uuid_value = (char *)malloc(40);
    uuid_generate(new_uuid);
    uuid_unparse(new_uuid, uuid_value);
    std::string dt_now(uuid_value);
    free(uuid_value);
    uuid_value = nullptr;
    return dt_now;
}

void util::print_log(std::string msg)
{
    std::cout << get_time_now() << ",finished in " << msg << std::endl;
}

void util::operator_override(){
    book bk(static_cast<uint64_t>(10*10),static_cast<uint64_t>(10*10),get_uuid(),get_uuid(),get_uuid(),
    get_uuid(),get_uuid(),get_uuid(),get_uuid(),get_uuid(),get_uuid());
    bk.print_book(bk);
    book another_book;
    another_book=bk;
    another_book.print_book(another_book);
    std::cout<<std::endl<<std::endl;
    std::cout<<"The original address "<<&bk<<std::endl;
    std::cout<<"The assigned address "<<&another_book<<std::endl;
    std::cout<<std::endl<<std::endl;
    std::stringstream ss;
    ss << __FUNCTION__ << "," << __LINE__ << std::endl;
    print_log(ss.str());
}

g++ -g -std=c++2a -I. *.cpp ./model/*.cpp -o h1 -luuid -lpthread