Callbacks overview in Ruby on Rails - Step-by-Step Execution

Concept Flow - Callbacks overview

Object Created

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Before Validation Callback

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Validation

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After Validation Callback

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Before Save Callback

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Before Create or Update Callback

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Save to Database

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After Create or Update Callback

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After Save Callback

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After Commit Callback

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Object Ready

Rails callbacks run in a specific order around object lifecycle events like validation and saving, allowing code to run before or after these steps.

Execution Sample

Ruby on Rails

class User < ApplicationRecord
  before_save :normalize_name
  after_create :send_welcome_email

  def normalize_name
    self.name = name.strip.titleize
  end

  def send_welcome_email
    EmailService.send_welcome(self)
  end
end

This code runs a method to clean the user's name before saving and sends a welcome email after creating the user.

Execution Table

Step	Callback/Event	Action	Effect on Object	Notes
1	Object Created	New User instance initialized	User object with raw name	Start of lifecycle
2	before_save	normalize_name called	Name trimmed and capitalized	Runs before saving to DB
3	Validation	Validates user data	Checks if user data is valid	If invalid, save stops
4	Save to Database	User record saved	User data stored in DB	Persisted user
5	after_create	send_welcome_email called	Welcome email sent	Runs only on new record creation
6	after_save	Callback chain ends	User object saved and callbacks done	Final step
7	after_commit	Transaction committed	Changes finalized	Ensures DB transaction success
8	End	Lifecycle complete	User ready for use	No more callbacks

💡 All callbacks run in order around save; process ends after after_commit

Variable Tracker

Variable	Start	After before_save	After Validation	After Save	After after_create	Final
user.name	" alice "	"Alice"	"Alice"	"Alice"	"Alice"	"Alice"
user.persisted?	false	false	false	true	true	true
email_sent	false	false	false	false	true	true

Key Moments - 3 Insights

Why does the name change after before_save but before validation?

The execution_table shows before_save runs before validation, so normalize_name cleans the name before validations check it.

When is the welcome email sent in the lifecycle?

The after_create callback runs only after the user is saved for the first time, as shown in step 5 of the execution_table.

What happens if validation fails?

Validation happens after before_save; if it fails, the save and subsequent callbacks like after_create do not run, stopping the process early.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of user.name after the before_save callback?

A "Alice"

B " alice "

C "ALICE"

D "alice"

💡 Hint

Check the 'After before_save' column for user.name in variable_tracker.

At which step does the user record get saved to the database?

A Step 3

B Step 4

C Step 5

D Step 6

💡 Hint

Look at the 'Save to Database' event in the execution_table.

If validation fails, which callback will NOT run?

A before_validation

B before_save

C after_create

D after_commit

💡 Hint

Refer to the key_moments about validation failure stopping save and after_create callbacks.

Concept Snapshot

Rails callbacks run around object lifecycle events.
Common callbacks: before_save, after_create, after_commit.
before_save runs before validation and saving.
after_create runs only after new record creation.
Use callbacks to run code automatically at these points.

Full Transcript

Rails callbacks are special methods that run automatically at certain points in an object's lifecycle, like before saving or after creating a record. For example, before_save runs a method to clean data before the object is saved to the database. After_create runs a method to send a welcome email only after the object is first saved. The callbacks run in a specific order: object creation, before_save, validation, saving, after_create, after_save, and after_commit. If validation fails, the save and later callbacks do not run. This lets you add automatic behaviors tied to saving and creating objects in Rails.