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Mauricio Ackermann
Mauricio Ackermann

Posted on • Originally published at mauricioackermann.com.br on

How to preview emails with ActionMailer::Preview on Rails

#rails #ruby

We know how it's a pain to test ** e-mails** in our dev environment. Thinking of it, on Rails 4.1, the ActionMailer::Preview was released, making it possible to view e-mails without actually sending them. Let's learn how to use this tool.

First of all, we need to create a new mailer in our project.

rails generate mailer Welcome Running via Spring preloader in process 5087 create app/mailers/welcome_mailer.rb invoke erb create app/views/welcome_mailer invoke test_unit create test/mailers/welcome_mailer_test.rb create test/mailers/previews/welcome_mailer_preview.rb
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It's possible to see that Rails created to files inside test filter: test/mailers/welcome_mailer_test.rb and test/mailers/previews/welcome_mailer_preview.rb. In our case, we are going to use test/mailers/previews/welcome_mailer_preview.rb to preview our templates.

Now let's create a method inside WelcomeMailer that will be responsible for sending a welcome message to users that signup in our system, assuming we have a model User with an e-mail attribute. To do that, we need to open the file app/mailers/welcome_mailer.rb

class WelcomeMailer < ApplicationMailer def send_welcome_email(user) @user = user mail({ to: user.email, from: 'eu@mauricioackermann.com.br', subject: 'Seja bem-vindo ao sistema Maurício Ackermann' }) end end
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Since WelcomeMailer is inheriting from ApplicationMailer, he will use the mailer default layout

class ApplicationMailer < ActionMailer::Base default from: 'from@example.com' layout 'mailer' end
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app/layouts/mailer.html.erb

<!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <style> /* Email styles need to be inline */ </style> </head> <body> <%= yield %> </body> </html>
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At last, we need to create an e-mail template. Let's create a file send_welcome_email.html.erb inside the folder app/views/welcome_mailer, which will be our e-mail view.

<p>Hello, <%= @user.name %></p> <p><strong>Thank you</strong> for registering in our system!</p>
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Now that we have our mailer and template done let's test it. All e-mail previews are in test/mailers/previews. Open the file created by our generator, welcome_mailer_preview.html.erb.

class WelcomeMailerPreview < ActionMailer::Preview def send_welcome_email WelcomeMailer.send_welcome_email(User.new(name: 'Maurício Ackermann', email: 'eu@mauricioackermann.com.br')) end end
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Now to visualize the e-mail, we start the server and access the link
http://localhost:3000/rails/mailers/welcome_mailer/send_welcome_email

Did you know about this Rails feature? I hope this post helps you debugging your projects

Top comments (4)

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bizzibody profile image
Ian bradbury •

I never knew that. Thanks.

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mbackermann profile image
Mauricio Ackermann •

It's a great tool. I use it a lot

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jattoabdul profile image
Jatto Abdulqahhar •

Can this be used in previewing emails in staging environments?

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mbackermann profile image
Mauricio Ackermann •

Absolutely! You can turn it on on any envrionment. You can use the following config:

config.action_mailer.show_previews = true
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