Action Mailer Basics

What's a mailer?

Action Mailer allows you to send emails from your application using mailer classes and views.

Mailers work very similarly to controllers. They live in app/mailers, and have associated views.

Let's set up a new project. The user story will be: When a new user signs up they immediately receive a welcome email. 

$ rails new mailer

Generate a mailer

Let's generate a mailer using the command below:

$ rails generate mailer UserMailer

This gives us 2 rb files in app/mailers, 2 html.erb files in views/layouts and a user_mailer folder under views:

controller-like

Where a controller generates content like HTML to send back to the client, a Mailer creates a message to be delivered via email. Let's add a welcome_email action to our mailers/user_mailer.rb file:

class UserMailer < ApplicationMailer
  default from: 'notifications@example.com'
 
  def welcome_email(user)
    @user = user
    @url  = 'http://example.com/login'
    mail(to: @user.email, subject: 'Welcome to My Awesome Site')
  end
end

email HTML view

Now let's actually create the email in a view. We'll create a brand new file under app/views/user_mailer called "welcome_email.html.erb" (the name must exactly match the method we wrote in the mailer rb)

<h1>Welcome to example.com, <%= @user.name %></h1>
<p>
  You have successfully signed up to example.com, 
  your username is: <%= @user.login %>.<br>
</p>
<p>
  To login to the site, just follow this link: <%= @url %>.
</p>
<p>Thanks for joining and have a great day!</p>

Why don't we need the html and body tags?

email Text view

Let's also create a text-only version for our friends who use email clients that don't except HTML emails. This file will be called "welcome.text.erb"

Welcome to example.com, <%= @user.name %>
===============================================
 
You have successfully signed up to example.com,
your username is: <%= @user.login %>.
 
To login to the site, just follow this link: <%= @url %>.
 
Thanks for joining and have a great day!

Generating users

Let's scaffold a User with name, email and login fields.

$ rails generate scaffold User name email login
$ rake db:migrate

Calling the mailer

Then add the following line to users_controller.rb so that the email will be sent out upon user creation.

 def create
    @user = User.new(user_params)

    respond_to do |format|
      if @user.save
        # Tell the UserMailer to send a welcome email after save
        UserMailer.welcome_email(@user).deliver_now
...

Config

In order to actually send an email through gmail we need to set up our SMTP settings in config/development.rb

  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = {
    address:     'smtp.gmail.com',
    port:        587,
    domain:      'gmail.com',
    user_name:   'USERNAME@gmail.com',
    password:     'YOUR_ACTUAL_PASSWORD_HERE_SERIOUSLY', 
    authentication:  'plain',
    enable_starttls_auto: true
  }

SMTP = Simple Mail Transfer Protocol

Preview the email

Take the steps below to preview the email

• Add a user to localhost:3000/users
   
• Write the following action in test/mailers/previews/user_mailer_preview.rb
   
• Browse the page at the URL specified in the comment

# Preview all emails at http://localhost:3000/rails/mailers/user_mailer

class UserMailerPreview < ActionMailer::Preview
  def user_mail_preview
    UserMailer.welcome_email(User.first)
  end
end

test iT

Go ahead and browse to localhost:3000/users and add a user (you!) with your personal email address. In a few seconds you should receive an email in your inbox:

A preview of the html will also appear in the terminal:

Production setup

To get this working on production you'll have to copy the config settings in config/development.rb to config/production.rb.

Additionally you'll want to install the figaro gem in order to hide your gmail credentials in environment variables.