Action Mailer setup in Ruby on Rails - Mini Project: Build & Apply

Action Mailer setup

📖 Scenario: You are building a simple Rails app that needs to send emails to users. To do this, you will set up Action Mailer, which is the tool Rails uses to send emails.Imagine you want to send a welcome email to new users after they sign up.

🎯 Goal: Set up Action Mailer in a Rails app by creating a mailer class, configuring the default sender email, and defining a welcome email method.

📋 What You'll Learn

Create a mailer class named UserMailer

Set the default from email address to [e-mail]

Define a method welcome_email that takes a user parameter

Set the recipient email to user.email and the subject to Welcome to MyApp!

💡 Why This Matters

🌍 Real World

Sending emails like welcome messages, notifications, or password resets is common in web apps to communicate with users.

💼 Career

Understanding Action Mailer setup is essential for Rails developers to implement email features in real projects.

1

Create the mailer class

Create a mailer class called UserMailer that inherits from ApplicationMailer.

Ruby on Rails

# Create the UserMailer class inheriting from ApplicationMailer
# Your code here

Hint

Use class UserMailer < ApplicationMailer to start the mailer class.

2

Set default sender email

Inside the UserMailer class, set the default from email address to '[e-mail]' using default from:.

Ruby on Rails

class UserMailer < ApplicationMailer
  # Set default from email
  # Your code here
end

Hint

Use default from: '[e-mail]' inside the class.

3

Define the welcome_email method

Add a method called welcome_email inside UserMailer that takes a user parameter. Inside it, set @user = user and call mail with to: @user.email and subject: 'Welcome to MyApp!'.

Ruby on Rails

class UserMailer < ApplicationMailer
  default from: '[e-mail]'

  # Define welcome_email method
  # Your code here
end

Hint

Define def welcome_email(user), assign @user = user, then call mail(to: @user.email, subject: 'Welcome to MyApp!').

4

Complete the mailer setup

Ensure the UserMailer class is properly closed with end and ready to be used to send emails.

Ruby on Rails

class UserMailer < ApplicationMailer
  default from: '[e-mail]'

  def welcome_email(user)
    @user = user
    mail(to: @user.email, subject: 'Welcome to MyApp!')
  end
  # Ensure class is closed
end

Hint

Check that the class and method are properly closed with end.

Practice

1. What is the main purpose of Action Mailer in a Rails application?

easy

A. To manage database migrations automatically

B. To send emails by defining mailer classes and methods

C. To handle user authentication and sessions

D. To style HTML views with CSS

Solution

1. Step 1: Understand Action Mailer role

   Action Mailer is designed to send emails by organizing mailer classes and methods.

2. Step 2: Compare with other Rails features

   Database migrations, authentication, and styling are handled by other parts of Rails, not Action Mailer.

3. Final Answer:

   To send emails by defining mailer classes and methods -> Option B

4. Quick Check:

   Action Mailer = send emails [OK]

Hint: Remember: Action Mailer is for emails, not database or styling [OK]

Common Mistakes:

• Confusing Action Mailer with Active Record migrations
• Thinking it handles user login or CSS styling
• Assuming it manages background jobs directly

2. Which of the following is the correct way to define a mailer method in a Rails mailer class?

easy

A. def welcome_email(user) mail to: user.email, subject: 'Welcome' end

B. def welcome_email(user) { send_email(to: user.email) }

C. def welcome_email(user) mail(to user.email, subject 'Welcome') end

D. def welcome_email(user); mail(to: user.email, subject: 'Welcome'); end

Solution

1. Step 1: Check Ruby method syntax

   Method definitions use def name(params); ...; end with parentheses and semicolons optional but recommended for clarity.

2. Step 2: Verify mail method usage

   The mail method requires keyword arguments with colons, e.g., to: user.email, and commas between arguments.

3. Final Answer:

   def welcome_email(user); mail(to: user.email, subject: 'Welcome'); end -> Option D

4. Quick Check:

   Correct Ruby method and mail syntax = def welcome_email(user); mail(to: user.email, subject: 'Welcome'); end [OK]

Hint: Use parentheses and colons for keyword args in mail method [OK]

Common Mistakes:

• Missing parentheses or commas in method definition
• Using braces {} instead of do...end or semicolons
• Omitting colons in keyword arguments

3. Given this mailer method in Rails:

class UserMailer < ApplicationMailer
  def notify(user)
    mail(to: user.email, subject: 'Notice')
  end
end

What will happen when you call UserMailer.notify(user).deliver_now?

medium

A. An email is sent immediately to the user's email address

B. An email is queued but not sent until later

C. A syntax error occurs because deliver_now is invalid

D. Nothing happens because notify method lacks a body

Solution

1. Step 1: Understand deliver_now behavior

   The deliver_now method sends the email immediately when called on a mail object.

2. Step 2: Check mailer method correctness

   The notify method calls mail with valid parameters, so it returns a mail object ready to send.

3. Final Answer:

   An email is sent immediately to the user's email address -> Option A

4. Quick Check:

   deliver_now sends email immediately = An email is sent immediately to the user's email address [OK]

Hint: deliver_now sends email immediately, deliver_later queues it [OK]

Common Mistakes:

• Confusing deliver_now with deliver_later
• Thinking mail method sends email by itself
• Assuming notify method must have email body text

4. You wrote this mailer method:

def alert(user)
  mail(to: user.email, subject: 'Alert')
end

But emails are not sending. Which is the most likely cause?

medium

A. SMTP settings are not configured properly in environment files

B. The mail method is missing a block with email body content

C. You forgot to call deliver_now or deliver_later

D. Mailer class must inherit from ActionMailer::Base explicitly

Solution

1. Step 1: Check SMTP configuration

   Without proper SMTP settings, emails cannot be sent even if mailer code is correct.

2. Step 2: Review other options

   Mailer inheritance from ApplicationMailer is standard; mail method can use templates for body; calling deliver_now is needed but question implies method is called.

3. Final Answer:

   SMTP settings are not configured properly in environment files -> Option A

4. Quick Check:

   SMTP config missing = emails not sent [OK]

Hint: Check SMTP setup first if emails don't send [OK]

Common Mistakes:

• Assuming mail method sends email without deliver_now
• Forgetting to configure SMTP in config/environments
• Thinking mailer must inherit directly from ActionMailer::Base

5. You want to configure Action Mailer to send emails via Gmail SMTP in production. Which configuration snippet in config/environments/production.rb is correct?

hard

A. config.action_mailer.smtp_settings = { address: 'smtp.gmail.com', port: 587, domain: 'gmail.com', user_name: ENV['GMAIL_USERNAME'], password: ENV['GMAIL_PASSWORD'], authentication: 'plain' }

B. config.action_mailer.smtp_settings = { address: 'smtp.gmail.com', port: 25, domain: 'gmail.com', user_name: 'user', password: 'pass', authentication: 'login', enable_ssl: true }

C. config.action_mailer.smtp_settings = { address: 'smtp.gmail.com', port: 587, domain: 'yourdomain.com', user_name: ENV['GMAIL_USERNAME'], password: ENV['GMAIL_PASSWORD'], authentication: 'plain', enable_starttls_auto: true }

D. config.action_mailer.smtp_settings = { address: 'smtp.gmail.com', port: 465, domain: 'yourdomain.com', user_name: ENV['GMAIL_USERNAME'], password: ENV['GMAIL_PASSWORD'], authentication: 'plain', enable_starttls_auto: false }

Solution

1. Step 1: Identify correct SMTP port and security

   Gmail SMTP uses port 587 with STARTTLS enabled (enable_starttls_auto: true) for secure email sending.

2. Step 2: Check domain and authentication

   Domain should be your app's domain, authentication 'plain' is standard, and credentials should come from environment variables for security.

3. Final Answer:

   config.action_mailer.smtp_settings = { address: 'smtp.gmail.com', port: 587, domain: 'yourdomain.com', user_name: ENV['GMAIL_USERNAME'], password: ENV['GMAIL_PASSWORD'], authentication: 'plain', enable_starttls_auto: true } -> Option C

4. Quick Check:

   Gmail SMTP with port 587 and STARTTLS = config.action_mailer.smtp_settings = { address: 'smtp.gmail.com', port: 587, domain: 'yourdomain.com', user_name: ENV['GMAIL_USERNAME'], password: ENV['GMAIL_PASSWORD'], authentication: 'plain', enable_starttls_auto: true } [OK]

Hint: Use port 587 and enable_starttls_auto true for Gmail SMTP [OK]

Common Mistakes:

• Using wrong port like 25 or 465 without proper TLS
• Setting domain to 'gmail.com' instead of your app domain
• Omitting enable_starttls_auto or setting it false