Rails 4.1 Mailer Previews and Devise custom emails

Question

I have a brand new Rails 4.1.1 app where I'm customizing the Devise emails. I want to have them displayed on the new Rails email preview feature so I did the following:

1) Added the following snippet to my config/development.rb file:

config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews"

2) Created my custom Devise email UserMailer in app/mailers/user_mailer.rb:

class UserMailer < Devise::Mailer   
  helper :application # gives access to all helpers defined within `application_helper`.
  include Devise::Controllers::UrlHelpers # Optional. eg. `confirmation_url`

  layout "notifications_mailer"
end

3) Changed config/initializers/devise.rb to contain the following snippet:

config.mailer = 'UserMailer'

4) Added the class UserMailerPreview to lib/mailer_previews with the following content:

class UserMailerPreview < ActionMailer::Preview
  def confirmation_instructions
    UserMailer.confirmation_instructions(User.first, {})
  end

  def reset_password_instructions
    UserMailer.reset_password_instructions(User.first, {})
  end

  def unlock_instructions
    UserMailer.unlock_instructions(User.first, {})
  end
end

So far, so good. Looks like I've done everything right. But then I try to see the preview for the confirmation_instructions email at the /rails/mailers/user_mailer/confirmation_instructions route and I get the following error:

undefined method `confirmation_url' for #<#<Class:0x007fa02ab808e0>:0x007fa030fb7e80>

the code for my confirmation_url.html.erb template looks like this:

<%= t("notifications.texts.greeting") + @user.display_name %>,

<p>You can confirm your account email through the link below:</p>

<p><%= link_to 'Confirm my account', confirmation_url(@resource, :confirmation_token =>  @token) %></p>

What am I doing wrong? I guess it is something wrong with the way I call the confirmation_url method. Anyone can help me here?

Answer 1

For those looking to preview Devise emails without using custom mailers, (but still custom emails) this is what I did:

1. Configure your app for email previewing.

2. Set up the Devise Mailer Preview class

   a. Rails ~> 4.1

   # mailer/previews/devise_mailer_preview.rb
   class Devise::MailerPreview < ActionMailer::Preview
   
     def confirmation_instructions
       Devise::Mailer.confirmation_instructions(User.first, "faketoken")
     end
   
     def reset_password_instructions
       Devise::Mailer.reset_password_instructions(User.first, "faketoken")
     end
   
     ...
   
   end
   

   b. Rails ~> 5.0

   class DeviseMailerPreview < ActionMailer::Preview
   
     ... # same setup as Rails 4 above
   

3. Restart the server