Sending emails from controllers in Ruby on Rails - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the role of a mailer in Rails when sending emails from controllers?

A mailer in Rails is a special class designed to handle email creation and delivery. Controllers call mailer methods to send emails, keeping email logic separate from controller actions.

beginner

How do you trigger an email to be sent from a Rails controller?

You call a mailer method and then use .deliver_now or .deliver_later to send the email immediately or enqueue it for later delivery.

intermediate

What is the difference between deliver_now and deliver_later in Rails mailers?

deliver_now sends the email immediately during the request, which can slow down response time. deliver_later uses Active Job to send the email asynchronously, improving user experience.

beginner

Why should email sending logic be placed in mailers instead of directly in controllers?

Separating email logic into mailers keeps controllers clean and focused on handling web requests. It also makes email code reusable, easier to test, and maintain.

beginner

What is a typical method signature inside a Rails mailer for sending a welcome email?

A typical mailer method looks like this:
def welcome_email(user)
@user = user
mail(to: @user.email, subject: 'Welcome!')
end
This sets up the email recipient and subject.

Which method sends an email immediately from a Rails mailer?

A deliver_now

B send_email

C deliver_later

D send_now

deliver_now sends the email immediately. deliver_later queues it for later.

Where should email sending logic be placed in a Rails app?

A In the controller

B In the mailer

C In the view

D In the model

Email logic belongs in mailers to keep controllers clean and code reusable.

What does deliver_later do in Rails mailers?

A Sends email immediately

B Cancels email sending

C Saves email as draft

D Queues email to send asynchronously

deliver_later uses Active Job to send emails in the background.

How do you call a mailer method named notification_email for a user in a controller?

A NotificationMailer.notification_email(user).deliver_now

B notification_email(user).send()

C send_email(user)

D Mailer.notification_email(user)

You call the mailer class method and chain deliver_now or deliver_later.

Why might you prefer deliver_later over deliver_now?

A It sends emails faster

B It cancels emails automatically

C It improves user experience by not blocking the request

D It formats emails better

deliver_later sends emails asynchronously, so the user doesn't wait for email sending.

Explain how to send an email from a Rails controller using a mailer.

Think about separation of concerns and how Rails mailers work.

Describe the benefits of using deliver_later instead of deliver_now in Rails email sending.

Consider what happens during a web request when sending emails.

Practice

1. What is the main role of a controller when sending emails in Rails?

easy

A. To call the mailer method and trigger the email sending

B. To write the email content and layout

C. To configure the SMTP settings

D. To store email templates in the database

Solution

1. Step 1: Understand controller responsibility

   Controllers handle user requests and trigger actions like sending emails by calling mailer methods.

2. Step 2: Identify mailer role

   Mailers contain email content and setup, not controllers.

3. Final Answer:

   To call the mailer method and trigger the email sending -> Option A

4. Quick Check:

   Controllers trigger mailers [OK]

Hint: Controllers trigger mailers, mailers build emails [OK]

Common Mistakes:

• Writing email content in controllers
• Configuring SMTP in controllers
• Storing templates in controllers

2. Which of the following is the correct syntax to send an email immediately from a controller using a mailer named UserMailer and a method welcome_email?

easy

A. UserMailer.welcome_email.deliver_later(params[:user])

B. UserMailer.welcome_email(params[:user]).deliver_now

C. UserMailer.deliver_now.welcome_email(params[:user])

D. UserMailer.welcome_email(params[:user]).send_now

Solution

1. Step 1: Identify mailer method call

   The mailer method is called with parameters: UserMailer.welcome_email(params[:user]).

2. Step 2: Use correct delivery method

   To send immediately, use deliver_now after the mailer method call.

3. Final Answer:

   UserMailer.welcome_email(params[:user]).deliver_now -> Option B

4. Quick Check:

   Immediate send = deliver_now after mailer call [OK]

Hint: Call mailer method then add .deliver_now for immediate send [OK]

Common Mistakes:

• Using deliver_later for immediate send
• Calling deliver_now before mailer method
• Using non-existent send_now method

3. Given this controller code snippet:

def create
  @user = User.new(user_params)
  if @user.save
    UserMailer.welcome_email(@user).deliver_later
    redirect_to root_path, notice: 'User created!'

What happens when this code runs successfully?

medium

A. The welcome email is sent immediately before redirecting

B. The redirect happens only after the email is sent

C. The welcome email is queued to be sent later, then redirect happens

D. The email is never sent because deliver_later is incorrect here

Solution

1. Step 1: Understand deliver_later behavior

   Calling deliver_later queues the email to be sent asynchronously in the background.

2. Step 2: Analyze controller flow

   The redirect happens immediately after queuing the email, not waiting for sending.

3. Final Answer:

   The welcome email is queued to be sent later, then redirect happens -> Option C

4. Quick Check:

   deliver_later queues email, redirect immediate [OK]

Hint: deliver_later queues email, does not block controller [OK]

Common Mistakes:

• Thinking deliver_later sends email immediately
• Assuming redirect waits for email sending
• Believing deliver_later is invalid syntax

4. Identify the error in this controller code snippet:

def notify
  UserMailer.notify_user.deliver_now(user)
  redirect_to dashboard_path
end

medium

A. deliver_now is not a valid method for sending emails

B. redirect_to should be called before sending email

C. notify_user method cannot be called without parentheses

D. deliver_now should be called after passing user argument to notify_user

Solution

1. Step 1: Check method call order

   The user argument must be passed to notify_user before calling deliver_now.

2. Step 2: Correct syntax

   Correct call: UserMailer.notify_user(user).deliver_now.

3. Final Answer:

   deliver_now should be called after passing user argument to notify_user -> Option D

4. Quick Check:

   Pass args before deliver_now [OK]

Hint: Pass arguments inside mailer method, then call deliver_now [OK]

Common Mistakes:

• Calling deliver_now with arguments
• Calling redirect_to before email
• Misusing parentheses in method calls

5. You want to send a confirmation email from a controller only if the user has a verified email address. Which is the best way to implement this?

hard

A. In the controller, check if user.verified? then call UserMailer.confirmation_email(user).deliver_now

B. Always call UserMailer.confirmation_email(user).deliver_now and check verification inside the mailer

C. Send the email unconditionally and add a condition in the email template

D. Call UserMailer.confirmation_email.deliver_now(user) without any condition

Solution

1. Step 1: Decide where to check condition

   Controller should decide if email should be sent based on user verification status.

2. Step 2: Call mailer only when condition is true

   Call UserMailer.confirmation_email(user).deliver_now only if user.verified? is true.

3. Final Answer:

   In the controller, check if user.verified? then call UserMailer.confirmation_email(user).deliver_now -> Option A

4. Quick Check:

   Check condition in controller before sending email [OK]

Hint: Check conditions in controller before calling mailer [OK]

Common Mistakes:

• Checking conditions inside mailer or template
• Sending emails unconditionally
• Passing arguments after deliver_now