Access compute_asset_host from inside a rake task?

I've tried including ActionView::Helpers::AssetTagHelper and a bunch of variants of that, but I always get an error saying NameError: undefined local variable or methodconfig' for main:Object`

Updated with more info

I need to be able to reference a resource that is stored on different servers depending on the environment. On my development machine it will be referenced at localhost:3000, on the production server it will be at one CDN address, and on staging it will be at yet another. Obviously we want to test this rake task locally first, then on staging and then finally on staging so the rake tasks needs to be able to generate URLs based on the asset host configuration variable. I actually went so far as to create an ApplicationHelper method called asset_path to do this in my views, but it's basically just an alias for compute_asset_host. However, if I include Applicati开发者_如何转开发onHelper in my rake task and call asset_path it complains that compute_public_path is undefined, and then if I include (or extend) ActionView::Helpers::AssetTagHelper it complains about undefined local variable or method 'config' for main:Object from inside compute_asset_host. So I need to somehow invoke whatever instantiates the config container that is used by ActionView::Helpers so that compute_asset_host can return the proper URL based on the environment.

It is ugly and I try to get around doing things like this but...

namespace :test do

  def view(url_options = {}, *view_args)
    view_args[0] ||= ActionController::Base.view_paths
    view_args[1] ||= {}

    view = ActionView::Base.new(*view_args)
    routes = Rails::Application.routes
    routes.default_url_options = {:host => 'localhost'}.merge(url_options)

    view.class_eval do
      include ApplicationHelper
      include routes.url_helpers
    end

    assigns = instance_variables.inject(Hash.new) do |hash, name|
      hash.merge name[1..-1] => instance_variable_get(name)
    end
    view.assign assigns

    view
  end  

  task :it => :environment do
    param = ""
    puts ">>> compute_asset_host returns: [#{view.send("compute_asset_host", param)}]"
  end

end

... may start you in a direction to solve the problem you are having.

PS: I found the view method here: https://gist.github.com/592846

This is what I do

task :it => :environment do
  include ActionView::Helpers
  include ApplicationHelper
  # your code here
end