AWS to serve CSS images Sinatra - ruby

Question

I am using the asset_sync gem to sync my assets to a S3 bucket. In production i want to use S3 and in development i want to use my local files. So i have setup the following along with a helper
environments/development.rb
configure :development do
set :asset_host, "/"
end
environments/production.rb
configure :production do
set :asset_host, "https://s3-eu-west-1.amazonaws.com/#{ENV['FOG_DIRECTORY']}"
end
helper
helpers do
def aws_asset( path )
File.join settings.asset_host, path
end
end
So in my views i can do this
<%= image_tag( aws_asset "/assets/images/wd.png") %>
Which will result in rendering that image from my local assets if in development or from my bucket when in production
So what if i want to render an image from within my main.css file, such as a background image? I cant do the below for example as its not an erb file
main.css
header{
background: #ffffff url('<%= aws_asset("/assets/images/bgwRpeat.png") %>') repeat-x;
}
So what can I do? Has anyone done this before
Thanks for any help anyone can offer

Answer 1

3 ways come to mind.
Precompile the assets
Before you deploy, precompile the assets and CSS. If you create a file called main.css.erb and then run it through ERB to produce main.css it'll have the right stuff inside. This would be my preference. There are lots of ways to precompile, I prefer Guard but YMMV.
Edit:
Lifted and twisted from the Guard::Erb docs
guard 'erb', :input => 'app/views/stylesheets/main.css.erb', :output => "public/assets/stylesheets/main.css" do
watch (%r{app/views/stylesheets/main.css.erb})
end
Something like that.
Create a route that then compiles the assets
This is similar to how you might use SASS templates with Sinatra (if you don't precompile them). Just do the same as above, set up a route for main.css, run the main.css.erb template through ERB and serve it. Add lots of caching.
Edit:
get "/assets/stylesheets/main.css" do
# remember to look at caching
erb :"stylesheets/main.css"
end
I started writing and I can't remember the 3rd :) In my defence, I've a terrible headache. Perhaps someone else will remember for me.