Mailer generation and templates in Ruby on Rails - Step-by-Step Execution

Concept Flow - Mailer generation and templates

Generate Mailer with command

↓

Mailer class created

↓

Define mail method with subject, to, from

↓

Create email template file

↓

Render template with variables

↓

Send email via mailer method

↓

Email delivered to recipient

This flow shows how Rails generates a mailer, defines email methods, creates templates, and sends emails.

Execution Sample

Ruby on Rails

rails generate mailer UserMailer

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

This code generates a mailer and defines a welcome_email method that sends an email to a user.

Execution Table

Step	Action	Code/Command	Result/Output
1	Generate mailer	rails generate mailer UserMailer	Creates app/mailers/user_mailer.rb and views/user_mailer/
2	Define mail method	def welcome_email(user)...mail(...)	Method ready to send email with user data
3	Create template	app/views/user_mailer/welcome_email.html.erb	Template file for email body created
4	Call mailer method	UserMailer.welcome_email(user).deliver_now	Email object created and sent
5	Email sent	SMTP server processes email	User receives welcome email
6	Exit	No more mail to send	Process ends

💡 Mailer method called and email sent, no further actions

Variable Tracker

Variable	Start	After Step 2	After Step 4	Final
user	nil	User object passed in	User object passed in	User object passed in
@user	nil	User object assigned	User object assigned	User object assigned
mail object	nil	Mail::Message created	Mail::Message sent	Mail::Message sent

Key Moments - 3 Insights

Why do we need to create a template file after defining the mail method?

The mail method sets up the email headers, but the template file contains the actual email content. Without the template, the email body would be empty. See execution_table step 3.

What happens if we forget to call deliver_now or deliver_later on the mailer method?

The email is not sent automatically. The mail method only prepares the email object. Sending happens when deliver_now or deliver_later is called. See execution_table step 4.

How does the mailer know which template to use?

Rails uses the mail method name (like welcome_email) to find the matching template file in views/user_mailer/. See execution_table step 3.

Visual Quiz - 3 Questions

Look at the execution_table, at which step is the email template file created?

A Step 4

B Step 1

C Step 3

D Step 5

💡 Hint

Check the 'Action' column for template creation in execution_table

According to variable_tracker, what is the state of the mail object after step 4?

A nil

B Mail::Message sent

C User object assigned

D Mail::Message created

💡 Hint

Look at the 'mail object' row and 'After Step 4' column in variable_tracker

If we skip calling deliver_now on the mailer method, what will happen?

A Email will not be sent

B Email will be sent immediately

C Email will be queued for later

D Template will not be rendered

💡 Hint

Refer to key_moments about calling deliver_now or deliver_later

Concept Snapshot

Rails Mailer Generation & Templates:
- Generate mailer: rails generate mailer NameMailer
- Define mail method with mail(to:, subject:)
- Create matching template in views/name_mailer/method.html.erb
- Call mailer.method(args).deliver_now to send
- Template renders email body
- deliver_now triggers immediate send

Full Transcript

This visual execution shows how Rails mailers are generated and used. First, the mailer is created with a command, which sets up the mailer class and folder for templates. Then, a mail method is defined to specify email details like recipient and subject. Next, a template file is created to hold the email content. When the mailer method is called with deliver_now, Rails renders the template and sends the email. Variables like the user and mail object change state through these steps. Key points include the need for templates to provide email content and the requirement to call deliver_now to actually send the email.