Book and User Structs

Part of the Object Oriented Programming section of Coddy's GO journey — lesson 99 of 107.

Challenge

Easy

Let's build the core data models for our Library Management System! You'll create the foundational structs that represent books and library members, complete with constructor functions that initialize them with sensible defaults.

You'll organize your code across three files:

book.go: Define your Book struct with fields for ID, Title, Author, ISBN, and Available (boolean). Create a NewBook constructor function that takes the ID, title, author, and ISBN as parameters and returns a pointer to a new Book. New books should always start as available. Add an Info() method that returns the book's details in the format: [ID] "Title" by Author (ISBN: [isbn]) - Available: [true/false]
user.go: Define your User struct with fields for ID, Name, Email, and BorrowedBooks (a slice of strings to store book IDs). Create a NewUser constructor that takes ID, name, and email, returning a pointer to a new User with an empty borrowed books list. Add an Info() method that returns: Member: [Name] ([Email]) - Books borrowed: [count]
main.go: Bring your models together by creating books and users from input, then displaying their information.
Read the number of books, then for each book read its ID, title, author, and ISBN on separate lines. Next, read the number of users, and for each user read their ID, name, and email on separate lines.

Print each book's info on its own line, followed by each user's info on its own line.

The following inputs will be provided:

Number of books
For each book: ID, title, author, ISBN (each on separate lines)
Number of users
For each user: ID, name, email (each on separate lines)

For example, given:

2
B001
The Go Programming Language
Alan Donovan
978-0134190440
B002
Clean Code
Robert Martin
978-0132350884
1
U001
Alice Smith
alice@library.com

Your output should be:

[B001] "The Go Programming Language" by Alan Donovan (ISBN: 978-0134190440) - Available: true
[B002] "Clean Code" by Robert Martin (ISBN: 978-0132350884) - Available: true
Member: Alice Smith (alice@library.com) - Books borrowed: 0

And given:

1
B100
Design Patterns
Gang of Four
978-0201633610
2
U001
Bob Jones
bob@email.com
U002
Carol White
carol@email.com

Your output should be:

[B100] "Design Patterns" by Gang of Four (ISBN: 978-0201633610) - Available: true
Member: Bob Jones (bob@email.com) - Books borrowed: 0
Member: Carol White (carol@email.com) - Books borrowed: 0

Notice how the constructors handle default values—books start available and users start with zero borrowed books. This pattern of using constructor functions to ensure proper initialization is fundamental to building reliable systems!

Try it yourself

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func main() {
	reader := bufio.NewReader(os.Stdin)

	// Read number of books
	numBooksStr, _ := reader.ReadString('\n')
	numBooks, _ := strconv.Atoi(strings.TrimSpace(numBooksStr))

	// TODO: Create a slice to store books

	// Read each book's details
	for i := 0; i < numBooks; i++ {
		id, _ := reader.ReadString('\n')
		id = strings.TrimSpace(id)
		title, _ := reader.ReadString('\n')
		title = strings.TrimSpace(title)
		author, _ := reader.ReadString('\n')
		author = strings.TrimSpace(author)
		isbn, _ := reader.ReadString('\n')
		isbn = strings.TrimSpace(isbn)

		// TODO: Create a new book using NewBook constructor and add to slice
	}

	// Read number of users
	numUsersStr, _ := reader.ReadString('\n')
	numUsers, _ := strconv.Atoi(strings.TrimSpace(numUsersStr))

	// TODO: Create a slice to store users

	// Read each user's details
	for i := 0; i < numUsers; i++ {
		id, _ := reader.ReadString('\n')
		id = strings.TrimSpace(id)
		name, _ := reader.ReadString('\n')
		name = strings.TrimSpace(name)
		email, _ := reader.ReadString('\n')
		email = strings.TrimSpace(email)

		// TODO: Create a new user using NewUser constructor and add to slice
	}

	// TODO: Print each book's info using the Info() method

	// TODO: Print each user's info using the Info() method

	fmt.Println() // Placeholder - remove when implementing
}