Many-to-many with has_many through in Ruby on Rails - Mini Project: Build & Apply

Many-to-many with has_many through

📖 Scenario: You are building a simple library system where books can have many authors, and authors can write many books. You will use Rails associations to connect Book and Author models through a join model called Authorship.

🎯 Goal: Create a many-to-many relationship between Book and Author models using has_many :through association with the join model Authorship.

📋 What You'll Learn

Create a Book model with a title attribute

Create an Author model with a name attribute

Create an Authorship join model with book_id and author_id as foreign keys

Set up has_many :through associations in Book and Author models

Set up belongs_to associations in Authorship model

💡 Why This Matters

🌍 Real World

Many real-world apps need to connect two things that can have many links between them, like books and authors, students and courses, or users and roles.

💼 Career

Understanding has_many :through associations is essential for Rails developers to model complex data relationships cleanly and maintainably.

1

Create the initial models

Create three Rails models: Book with attribute title:string, Author with attribute name:string, and Authorship with attributes book_id:integer and author_id:integer.

Ruby on Rails

# Create Book, Author, and Authorship models with specified attributes
# Your code here

Need a hint?

Use rails generate model commands or create model files with the specified attributes.

2

Add belongs_to associations in Authorship

In the Authorship model, add belongs_to :book and belongs_to :author associations.

Ruby on Rails

class Book < ApplicationRecord
end

class Author < ApplicationRecord
end

class Authorship < ApplicationRecord
  # Add belongs_to associations here
  # Your code here
end

Need a hint?

Each Authorship belongs to one Book and one Author.

3

Add has_many through associations in Book and Author

In the Book model, add has_many :authorships and has_many :authors, through: :authorships. In the Author model, add has_many :authorships and has_many :books, through: :authorships.

Ruby on Rails

class Book < ApplicationRecord
  # Add has_many and has_many through associations here
  # Your code here
end

class Author < ApplicationRecord
  # Add has_many and has_many through associations here
  # Your code here
end

class Authorship < ApplicationRecord
  belongs_to :book
  belongs_to :author
end

Need a hint?

Use has_many :through to connect Book and Author through Authorship.

4

Complete the association setup

Ensure all models have the correct associations: Book and Author have has_many :authorships and has_many :through associations, and Authorship has belongs_to associations.

Ruby on Rails

# Review and finalize the association setup
# Your code here

Need a hint?

Double-check all associations are correctly set for the many-to-many relationship.