Many-to-many with has_many through in Ruby on Rails - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a many-to-many association using has_many through in a Rails model.

Ruby on Rails

class Author < ApplicationRecord
  has_many :author_books
  has_many :books, [1]: :author_books
end

Drag options to blanks, or click blank then click option'

Athrough

Bclass_name

Cdependent

Dsource

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'source' instead of 'through' causes Rails to look for a different association.

Forgetting the 'through' option breaks the many-to-many link.

The has_many association uses the through option to specify the join model for many-to-many relationships.

2fill in blank

medium

Complete the join model declaration to set up the many-to-many relationship.

Ruby on Rails

class AuthorBook < ApplicationRecord
  belongs_to :author
  belongs_to [1]
end

Drag options to blanks, or click blank then click option'

Abook

Bbooks

Cauthor

Dauthors

Attempts:

3 left

💡 Hint

Common Mistakes

Using plural form like 'books' causes errors.

Using the wrong model name breaks the association.

The join model belongs to both associated models. Here, it belongs to book (singular).

3fill in blank

hard

Fix the error in the Book model to correctly set up the many-to-many association.

Ruby on Rails

class Book < ApplicationRecord
  has_many :author_books
  has_many :authors, [1]: :author_books
end

Drag options to blanks, or click blank then click option'

Asource

Bthrough

Cdependent

Dclass_name

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'source' instead of 'through' causes Rails to fail to find the join model.

Omitting the option breaks the association.

The has_many association must use through to specify the join model for many-to-many relations.

4fill in blank

hard

Fill both blanks to complete the migration for the join table.

Ruby on Rails

class CreateAuthorBooks < ActiveRecord::Migration[6.1]
  def change
    create_table :author_books do |t|
      t.references :[1], null: false, foreign_key: true
      t.references :[2], null: false, foreign_key: true
      t.timestamps
    end
  end
end

Drag options to blanks, or click blank then click option'

Aauthor

Bauthors

Cbook

Dbooks

Attempts:

3 left

💡 Hint

Common Mistakes

Using plural names like 'authors' or 'books' in references causes migration errors.

Forgetting foreign_key: true disables database-level integrity.

The join table references the singular model names author and book to create foreign keys.

5fill in blank

hard

Fill all three blanks to complete the Author model with dependent destroy and source options.

Ruby on Rails

class Author < ApplicationRecord
  has_many :author_books, [1]: :destroy
  has_many :books, [2]: :author_books, [3]: :book
end

Drag options to blanks, or click blank then click option'

Adependent

Bthrough

Csource

Dclass_name

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting dependent causes orphan join records.

Mixing up source and through options.

Using class_name instead of source causes errors.

dependent: :destroy ensures join records are deleted when an author is deleted. through: :author_books sets the join model. source: :book tells Rails which association to use on the join model.