class Api::Mobile::HomeController < Api::Mobile::ApplicationController
  include ActionView::Helpers::AssetUrlHelper

  def index
    @items = [Api::Mobile::HomePageItem.new(
                type: 'image',
                image: image_url("api/mobile/home/tutor-with-student.jpg"))]
  end
end

app/assets/images/api/mobile/home/tutor-with-student.jpg

http://myhost.com/images/api/mobile/home/tutor-with-student.jpg

http://myhost.com/assets/api/mobile/home/tutor-with-student.jpg

ActionController::Base.helpers.asset_url("api/mobile/home/tutor-with-student.jpg", type: :image)

config.action_controller.asset_host='myhost.com'

def logo_url
    host_url = request.original_url.split(request.path).first
    asset_path = ActionController::Base.helpers.asset_url('logo.png')
    host_url + asset_path
end
# will return
=> "http://localhost:3000/assets/logo-40e3bf1e10f0c00393ac94f96ea127986955c166eb839266eb2ad6e63b42754c.png"`