创建一个 Library类，包含一个 Book向量和一个Patron向量。定义一个名为Transaction 的 struet，包含一个Book对象、一个Patron对象和一个本章中定义的Date对象，表示借阅记录。在 Library 类中定义一个Transaction向量。定义向图书馆添加图书、添加读者以及借出书籍的函数。当一个读者借出一本书时,保证Library对象中有此读者和这本书的记录,否则报告错误。然后检查读者是否欠费，如果欠费就报告一个错误,否则创建一个Transaction对象，将其放人Transaction向量中。定义一个返回包含所有欠费读者姓名的向量的函数。多文件程序，代码按文件给出

尊敬的用户，您的问题需要涉及多个文件，本回答将提供三个文件的代码示例：

1. Book.h

#ifndef BOOK_H
#define BOOK_H

#include <string>

class Book {
public:
    Book(std::string _title, std::string _author, std::string _isbn, bool _is_checked_out = false)
        : title(_title), author(_author), isbn(_isbn), is_checked_out(_is_checked_out) {}

    std::string get_title() const { return title; }
    std::string get_author() const { return author; }
    std::string get_isbn() const { return isbn; }
    bool get_is_checked_out() const { return is_checked_out; }
    void set_is_checked_out(bool _is_checked_out) { is_checked_out = _is_checked_out; }

private:
    std::string title;
    std::string author;
    std::string isbn;
    bool is_checked_out;
};

#endif

2. Patron.h

#ifndef PATRON_H
#define PATRON_H

#include <string>

class Patron {
public:
    Patron(std::string _name, std::string _card_number, double _fees_owed = 0.0)
        : name(_name), card_number(_card_number), fees_owed(_fees_owed) {}

    std::string get_name() const { return name; }
    std::string get_card_number() const { return card_number; }
    double get_fees_owed() const { return fees_owed; }
    void set_fees_owed(double _fees_owed) { fees_owed = _fees_owed; }

private:
    std::string name;
    std::string card_number;
    double fees_owed;
};

#endif

3. Library.h

#ifndef LIBRARY_H
#define LIBRARY_H

#include <vector>
#include "Book.h"
#include "Patron.h"
#include "Date.h"

struct Transaction {
    Book book;
    Patron patron;
    Date date;
};

class Library {
public:
    void add_book(Book book);
    void add_patron(Patron patron);
    void lend_book(Book book, Patron patron, Date date);
    std::vector<std::string> get_debtors() const;

private:
    std::vector<Book> books;
    std::vector<Patron> patrons;
    std::vector<Transaction> transactions;

    bool has_book(const Book& book) const;
    bool has_patron(const Patron& patron) const;
};

#endif

4. Library.cpp

#include "Library.h"
#include <algorithm>

void Library::add_book(Book book) {
    books.push_back(book);
}

void Library::add_patron(Patron patron) {
    patrons.push_back(patron);
}

void Library::lend_book(Book book, Patron patron, Date date) {
    if (!has_book(book) || !has_patron(patron)) {
        throw std::runtime_error("The book or patron does not exist in the library.");
    }
    if (book.get_is_checked_out()) {
        throw std::runtime_error("The book is already checked out.");
    }
    if (patron.get_fees_owed() > 0.0) {
        throw std::runtime_error("The patron owes fees and cannot borrow books.");
    }
    book.set_is_checked_out(true);
    transactions.push_back(Transaction{book, patron, date});
}

std::vector<std::string> Library::get_debtors() const {
    std::vector<std::string> result;
    std::for_each(patrons.begin(), patrons.end(), [&](const Patron& patron) {
        if (patron.get_fees_owed() > 0.0) {
            result.push_back(patron.get_name());
        }
    });
    return result;
}

bool Library::has_book(const Book& book) const {
    return std::find(books.begin(), books.end(), book) != books.end();
}

bool Library::has_patron(const Patron& patron) const {
    return std::find(patrons.begin(), patrons.end(), patron) != patrons.end();
}

5. Date.h

#ifndef DATE_H
#define DATE_H

#include <ctime>

class Date {
public:
    Date(int _year, int _month, int _day)
        : year(_year), month(_month), day(_day) {}

    int get_year() const { return year; }
    int get_month() const { return month; }
    int get_day() const { return day; }

private:
    int year;
    int month;
    int day;
};

#endif

注意：本示例代码仅供参考，可能存在错误或不足之处，具体实现方式需要根据实际情况进行调整。