HTTP/2 Server Push for Rails - Add Link preload headers for all CSS and image assets on your home page

preload_helper.rb

module PreloadHelper
  def compute_asset_path(*args)
    computed_path = super
    add_link_header_for_computed_asset_path(computed_path)
    computed_path
  end
  
  protected
  
  # Preload all CSS and images on the home index page.
  def add_link_header_for_computed_asset_path(path)
    return unless Rails.env.production? &&
        current_page?(controller: 'home', action: 'index')
    asset_type = case path
    when /\/home\/ie(8|9)/ then return # Skip IE CSS
    when /\.css(\?|$)/ then 'style'
    when /\.(svg|png|jpg)(\?|$)/ then 'img'
    else return
    end
    response.headers['Link'] ||= []
    response.headers['Link'] << "<#{path}>; rel=preload; as=#{asset_type}"
  end
end