Mailer generation and templates in Ruby on Rails - Mini Project: Build & Apply

Mailer generation and templates

📖 Scenario: You are building a simple Rails app that sends welcome emails to new users.To do this, you need to create a mailer and a template for the email content.

🎯 Goal: Create a mailer called UserMailer with a method welcome_email that sends an email to a user.Also, create a simple email template that shows a welcome message with the user's name.

📋 What You'll Learn

Generate a mailer named UserMailer

Add a method welcome_email that accepts a user parameter

Set the email to address to user.email

Set the email subject to 'Welcome to Our App!'

Create a view template for welcome_email that displays 'Hello, !'

💡 Why This Matters

🌍 Real World

Sending emails is common in web apps for welcoming users, notifications, and password resets.

💼 Career

Understanding mailers is essential for backend Rails developers working on user communication features.

1

Generate 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

Add the welcome_email method

Inside UserMailer, add a method called welcome_email that takes a user parameter.

Ruby on Rails

class UserMailer < ApplicationMailer
  # Define welcome_email method with user parameter
  # Your code here
end

Hint

Define a method with def welcome_email(user) inside the class.

3

Set email recipient and subject

Inside the welcome_email method, use mail to set the to address to user.email and the subject to 'Welcome to Our App!'.

Ruby on Rails

class UserMailer < ApplicationMailer
  def welcome_email(user)
    # Use mail to set to and subject
    # Your code here
  end
end

Hint

Use mail(to: user.email, subject: 'Welcome to Our App!') inside the method.

4

Create the email template

Create a view template file named welcome_email.html.erb inside app/views/user_mailer/ that displays the text 'Hello, <%= @user.name %>!'. Also, assign @user = user inside the welcome_email method.

Ruby on Rails

class UserMailer < ApplicationMailer
  def welcome_email(user)
    # Assign @user for the template
    # Your code here
    mail(to: user.email, subject: 'Welcome to Our App!')
  end
end

# Create welcome_email.html.erb in app/views/user_mailer/
# Your code here

Hint

Assign @user = user in the method and create the template with 'Hello, <%= @user.name %>!'.

Practice

1. What is the primary purpose of a mailer in a Rails application?

easy

A. To send emails from the application

B. To handle database migrations

C. To manage user sessions

D. To style HTML templates

Solution

1. Step 1: Understand the role of mailers

   Mailers in Rails are designed to send emails from the application to users or other recipients.

2. Step 2: Differentiate from other components

   Database migrations handle schema changes, sessions manage user logins, and styling is done in views or CSS, not mailers.

3. Final Answer:

   To send emails from the application -> Option A

4. Quick Check:

   Mailer = send emails [OK]

Hint: Mailers send emails, not handle data or styling [OK]

Common Mistakes:

• Confusing mailers with controllers
• Thinking mailers manage database
• Assuming mailers style HTML

2. Which Rails command correctly generates a mailer named UserMailer?

easy

A. rails generate controller UserMailer

B. rails generate mailer UserMailer

C. rails generate model UserMailer

D. rails generate job UserMailer

Solution

1. Step 1: Identify the correct generator for mailers

   The command rails generate mailer UserMailer creates a mailer class and related files.

2. Step 2: Understand other generators

   Controllers handle web requests, models handle data, and jobs handle background tasks, so those commands are incorrect for mailers.

3. Final Answer:

   rails generate mailer UserMailer -> Option B

4. Quick Check:

   Mailer generator uses 'mailer' keyword [OK]

Hint: Use 'rails generate mailer' to create mailers [OK]

Common Mistakes:

• Using controller generator for mailers
• Confusing model and mailer generators
• Typing job instead of mailer

3. Given this mailer method:

class UserMailer < ApplicationMailer
  def welcome_email(user)
    @user = user
    mail(to: @user.email, subject: 'Welcome!')
  end
end

What happens when UserMailer.welcome_email(@user).deliver_now is called?

medium

A. The email is queued but not sent immediately

B. The method returns a string with the email content but does not send it

C. An email is sent immediately to the user's email with subject 'Welcome!'

D. An error occurs because deliver_now is not a valid method

Solution

1. Step 1: Understand mailer method behavior

   The method welcome_email sets instance variables and calls mail to prepare the email.

2. Step 2: Effect of deliver_now

   Calling deliver_now sends the email immediately instead of queuing it.

3. Final Answer:

   An email is sent immediately to the user's email with subject 'Welcome!' -> Option C

4. Quick Check:

   deliver_now sends email immediately [OK]

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

Common Mistakes:

• Thinking deliver_now only prepares email
• Confusing deliver_now with deliver_later
• Assuming deliver_now is invalid

4. Identify the error in this mailer template file named welcome_email.html.erb:

<h1>Welcome, <%= @user.name %>!</h1>
<p>Thanks for joining.</p>
<p>Your email is: <%= user.email %></p>

medium

A. The = sign is missing in the ERB tags

B. The HTML tags are incorrect and will cause rendering errors

C. The template file should be named welcome_email.text.erb

D. The variable user is undefined; should use @user

Solution

1. Step 1: Check variable usage in template

   The mailer method sets @user, so the template must use @user to access user data.

2. Step 2: Identify incorrect variable

   The template uses user.email which is undefined, causing an error.

3. Final Answer:

   The variable user is undefined; should use @user -> Option D

4. Quick Check:

   Use instance variables (@user) in mailer templates [OK]

Hint: Mailer templates use instance vars like @user, not local vars [OK]

Common Mistakes:

• Using local variables instead of instance variables
• Misnaming template files
• Forgetting <%= in ERB tags

5. You want to send a welcome email with both HTML and plain text versions. Which setup correctly supports this in Rails mailers?

hard

A. Create welcome_email.html.erb and welcome_email.text.erb templates in the mailer views folder

B. Create only welcome_email.html.erb template; Rails auto-generates text version

C. Create welcome_email.erb with mixed HTML and text content

D. Create welcome_email.text.erb only; HTML is optional

Solution

1. Step 1: Understand multi-format email templates

   Rails supports sending emails with both HTML and plain text by providing separate templates named with .html.erb and .text.erb extensions.

2. Step 2: Why both templates are needed

   Some email clients prefer plain text, so having both ensures compatibility and better user experience.

3. Final Answer:

   Create welcome_email.html.erb and welcome_email.text.erb templates in the mailer views folder -> Option A

4. Quick Check:

   Both .html.erb and .text.erb templates needed for multi-format emails [OK]

Hint: Use both .html.erb and .text.erb templates for emails [OK]

Common Mistakes:

• Assuming Rails auto-generates text version
• Mixing HTML and text in one template
• Skipping plain text template