Description

A couple of notes:
● The vector::erase() function lets you delete an element of a vector, shifting over all the elements after it.
● You’ll see in Book.hpp a line that says “class Patron;”. That is a forward declaration. It doesn’t say anything about the definition of the Paton class, but it promises the compiler that there will be a type named Patron. The reason we don’t just say “#include Patron.hpp” is that both Book and Patron need to know about each other, but they can’t both #include the other because that would create a cyclic dependency.

Here are the .hpp files: Book.hpp, Patron.hpp and Library.hpp

Here are descriptions of the three classes:
Book:
● idCode – a unique identifier for a Book (think library bar code, not ISBN)
● title – cannot be assumed to be unique
● author – the idCode, title and author don’t need set methods, since they will never change after the object has been created, therefore these fields can be initialized directly within the constructor
● location – a Book can be either on the shelf, on the hold shelf, or checked out
● checkedOutBy – pointer to the Patron who has it checked out (if any)
● requestedBy – pointer to the Patron who has requested it (if any); a Book can only be requested by one Patron at a time
● dateCheckedOut – when a book is checked out, this will be set to the currentDate of the Library
● CHECK_OUT_LENGTH – constant that gives how long a Book can be checked out for
● constructor – takes an idCode, title and author; checkedOutBy and requestedBy should be initialized to NULL; a new Book should be on the shelf
● some get and set methods

Patron:
● idNum – a unique identifier for a Patron
● name – cannot be assumed to be unique
● checkedOutBooks – a vector of pointers to Books that Patron currently has checkedOut
● fineAmount – how much the Patron owes the Library in late fines (measured in dollars); this is allowed to go negative
● a constructor that takes an idNum and name and initializes fineAmount to zero
● some get and set methods
● addBook – adds the specified Book to checkedOutBooks
● removeBook – removes the specified Book from checkedOutBooks
● amendFine – a positive argument increases the fineAmount, a negative one decreases it

Library:
● holdings – a vector of pointers to Books in the Library
● members – a vector of pointers to Patrons in the Library
● a constructor that initializes the currentDate to zero
● addBook – adds the parameter to holdings
● addPatron – adds the parameter to members
● getBook – returns a pointer to the Book corresponding to the ID parameter, or NULL if no such Book is in the holdings
● getPatron – returns a pointer to the Patron corresponding to the ID parameter, or NULL if no such Patron is a member
● checkOutBook
○ if the specified Book is not in the Library, return “book not found”
○ if the specified Patron is not in the Library, return “patron not found”
○ if the specified Book is already checked out, return “book already checked out”
○ if the specified Book is on hold by another Patron, return “book on hold by other patron”
○ otherwise update the Book’s checkedOutBy, dateCheckedOut and Location; if the Book was on hold for this Patron, update requestedBy; update the Patron’s checkedOutBooks; return “check out successful”
● returnBook
○ if the specified Book is not in the Library, return “book not found”
○ if the Book is not checked out, return “book already in library”
○ update the Patron’s checkedOutBooks; update the Book’s location depending on whether another Patron has requested it; update the
Book’s checkedOutBy; return “return successful”
● requestBook
○ if the specified Book is not in the Library, return “book not found”
○ if the specified Patron is not in the Library, return “patron not found”
○ if the specified Book is already requested, return “book already on hold”
○ update the Book’s requestedBy; if the Book is on the shelf, update its location to on hold; return “request successful”
● payFine
○ takes as a parameter the amount that is being paid (not the negative of that amount)
○ if the specified Patron is not in the Library, return “patron not found”
○ use amendFine to update the Patron’s fine; return “payment successful”
● incrementCurrentDate
○ If a book is checked out on day 0, then on day 1, the patron has had it for 1 day. On day 21, the patron has had it for 21 days, so it is still not overdue. On day 22, the book is overdue and fines will be charged.
● be careful – a Book can be on request without its location being the hold shelf (if another Patron has it checked out);

One limited example of how your classes might be used is:
Book b1(“123”, “War and Peace”, “Tolstoy”);
Book b2(“234”, “Moby Dick”, “Melville”);
Book b3(“345”, “Phantom Tollbooth”, “Juster”);
Patron p1(“abc”, “Felicity”);
Patron p2(“bcd”, “Waldo”);
Library lib; lib.addBook(&b1); lib.addBook(&b2); lib.addBook(&b3); lib.addPatron(&p1); lib.addPatron(&p2); lib.checkOutBook(“bcd”, “234”); for (int i=0; i<7; i++) lib.incrementCurrentDate(); lib.checkOutBook(“bcd”, “123”); lib.checkOutBook(“abc”, “345”); for (int i=0; i<24; i++) lib.incrementCurrentDate(); lib.payFine(“bcd”, 0.4); double p1Fine = p1.getFineAmount(); double p2Fine = p2.getFineAmount();
This example obviously doesn’t include all of the functions described above. You are responsible for testing all of the required functions to make sure they operate as specified.

You must submit on TEACH: Book.cpp, Patron.cpp, and Library.cpp. You do not need to submit the .hpp files.

In the main method you use for testing, you should only need to #include Library.hpp. Remember that your compile command needs to list all four .cpp files.

Just to think about: There are six possible changes in the location of a Book. Can all six occur?

There are a lot of details here – it’s entirely possible I omitted something or mis-stated something. If you think that is the case, I encourage you to ask me about it.