How to display images in a Rails mailer email? - ruby-on-rails

Question

I have an app that sends an email when a user signs up. I've got the emails to send successfully but the images are not getting sent. I'm hosting on Heroku and using Sendgrid to send emails.
Here's my signup_email.html.erb view:
<tr>
<td style="padding: 20px 0; text-align: center">
<img
src="<%= Rails.application.config.action_mailer.default_url_options[:host] %>assets/email/logo.png"
width="200"
height="50"
alt="logo"
border="0"
style="height: auto; background: #dddddd; font-family: sans-serif; font-size: 15px; line-height: 15px; color: #555555;"
/>
</td>
</tr>
This is not an issue where the browser hides images by default because I've tested on various browsers and tried to show images. The image path in the email shows: heroku-root/assets/email/logo.png
Here's the signup user_mailer.rb:
class UserMailer < ActionMailer::Base
default from: "App <welcome#app.com>"
def signup_email(user)
#user = user
mail(:to => user.email, :subject => "Thank you for joining!")
end
end
I've precompiled assets with rake assets:precompile so the logo is stored in public/assets/email directory.
The production.rb setting:
# Don't fallback to assets pipeline if a precompiled asset is missed
config.assets.compile = false
# Generate digests for assets URLs
config.assets.digest = true
config.action_mailer.default_url_options = { :host => ENV['DEFAULT_MAILER_HOST'] }
config.action_mailer.delivery_method = :smtp
config.serve_static_assets = true
I've tried using the inline attachment method from the Rails documentation but emails weren't getting sent at all.
class UserMailer < ActionMailer::Base
default from: "App <welcome#app.com>"
def signup_email(user)
#user = user
attachments.inline["logo.png"] = File.read("#{Rails.root}app/assets/email/logo.png")
mail(:to => user.email, :subject => "Thank you for joining!")
end
end
In the view, I call the logo like this:
<%= image_tag(attachments['logo.png'].url) %>
With the method above the emails don't get sent at all and I get the error that it couldn't find the file logo.

Answer 1

You should just be able to use the regular old <%= image_tag("logo.png") %> helpers just like you would use in your views. You may need to set your asset_host so that it includes a full URL for the images in the emails since they aren't displayed in the browser under your domain.
# I believe these should do the trick:
config.action_controller.asset_host = 'http://localhost:3000'
config.action_mailer.asset_host = config.action_controller.asset_host