Callbacks overview in Ruby on Rails - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when a before_save callback returns false?

In Rails, if a before_save callback returns false, what is the effect on the save operation?

Ruby on Rails

class User < ApplicationRecord
  before_save :check_status

  def check_status
    return false if inactive?
  end
end

user = User.new(status: 'inactive')
user.save

A The save operation continues normally and the record is saved.

B The save operation is aborted and the record is not saved.

C An exception is raised stopping the save operation.

D The callback is ignored and save proceeds.

💡 Hint

Think about how returning false in a before_save callback affects the transaction.

In Rails, returning false from a before_save callback halts the callback chain and prevents the save operation from completing.

📝 Syntax

intermediate

Which syntax correctly defines an after_commit callback?

Choose the correct way to define an after_commit callback in a Rails model.

A after_commit :send_notification

B after_commit do send_notification end

C after_commit -> { send_notification }

D after_commit :send_notification, on: :create

💡 Hint

Consider the options for specifying when the callback runs.

The after_commit callback can specify the timing with on: :create, on: :update, or on: :destroy. Option D correctly uses this syntax.

🔧 Debug

advanced

Why does this before_destroy callback not prevent deletion?

Given the following model, why does the record still get deleted despite the before_destroy callback?

Ruby on Rails

class Post < ApplicationRecord
  before_destroy :check_if_published

  def check_if_published
    throw(:abort) if published?
  end
end

post = Post.find(1)
post.destroy

A The <code>published?</code> method always returns false, so deletion proceeds.

B The callback uses <code>throw(:abort)</code> which is correct, so the record should not be deleted.

C The callback should return false instead of throwing :abort to stop deletion.

D The callback is not registered properly because it lacks <code>self.</code> prefix.

💡 Hint

Check the condition inside the callback method.

If published? returns false, the throw(:abort) is never called, so the deletion proceeds.

❓ state_output

advanced

What is the value of status after save with after_save callback?

Consider this model with an after_save callback that changes an attribute. What is the value of status after save completes?

Ruby on Rails

class Task < ApplicationRecord
  after_save :mark_completed

  def mark_completed
    update_column(:status, 'completed')
  end
end

task = Task.create(status: 'pending')
task.reload
status_value = task.status

A "completed"

B Raises an error due to recursive update

C nil

D "pending"

💡 Hint

Think about when after_save runs and what update_column does.

The after_save callback runs after the initial save. The update_column updates the attribute directly in the database without callbacks, so after reload, status is "completed".

🧠 Conceptual

expert

Which callback ensures code runs only after a successful database commit?

In Rails, which callback guarantees that the code inside it runs only after the database transaction has been successfully committed?

A after_create

B after_save

C after_commit

D after_validation

💡 Hint

Think about the difference between saving and committing a transaction.

after_commit runs only after the database transaction is fully committed, ensuring data is saved permanently.