Dependent destroy and nullify in Ruby on Rails - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to make associated comments deleted when a post is deleted.

Ruby on Rails

class Post < ApplicationRecord
  has_many :comments, [1]
end

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

Adependent: :destroy

B:dependent => :destroy

Cdependent: :nullify

D:dependent => :nullify

Attempts:

3 left

💡 Hint

Common Mistakes

Using hash rocket syntax (:dependent => :destroy) instead of the newer symbol syntax.

Using :nullify instead of :destroy when you want to delete associated records.

In Rails, to delete associated records when the parent is deleted, use dependent: :destroy in the association.

2fill in blank

medium

Complete the code to nullify the user_id in posts when a user is deleted.

Ruby on Rails

class User < ApplicationRecord
  has_many :posts, [1]
end

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

Adependent: :destroy

Bdependent: :nullify

Cdependent: :restrict_with_error

Ddependent: :delete_all

Attempts:

3 left

💡 Hint

Common Mistakes

Using :destroy deletes the posts instead of nullifying the user_id.

Using :delete_all deletes posts without callbacks.

Using dependent: :nullify sets the foreign key to NULL instead of deleting the associated records.

3fill in blank

hard

Fix the error in the association to properly destroy comments when a post is deleted.

Ruby on Rails

class Post < ApplicationRecord
  has_many :comments, dependent: [1]
end

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

A:nullify

B:restrict_with_exception

C:destroy

D:delete_all

Attempts:

3 left

💡 Hint

Common Mistakes

Using :delete_all skips callbacks and may cause issues.

Using :nullify does not delete comments.

The :destroy option ensures callbacks run and associated comments are deleted.

4fill in blank

hard

Fill both blanks to nullify the foreign key and prevent deletion if posts exist.

Ruby on Rails

class User < ApplicationRecord
  has_many :posts, [1], [2]
end

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

Adependent: :nullify

Bdependent: :restrict_with_error

Cdependent: :destroy

Ddependent: :delete_all

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to use multiple dependent options in one association.

Confusing :destroy with :nullify.

Using dependent: :nullify sets foreign keys to null, and dependent: :restrict_with_error prevents deletion if posts exist. However, only one dependent option is allowed, so this is a trick question to understand options.

5fill in blank

hard

Fill all three blanks to create a hash of post titles and their comment counts, only for posts with comments.

Ruby on Rails

post_comment_counts = posts.each_with_object({}) { |[3], h| h[[1]] = [2] if [3].comments.any? }

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

Apost.title

Bpost.comments.count

Cpost

Dposts

Attempts:

3 left

💡 Hint

Common Mistakes

Using the collection name instead of the loop variable.

Using the wrong attribute for keys or values.

This uses each_with_object to build a hash where keys are post titles and values are the count of comments, only for posts with comments.