reload_metals.rb

# Portable monkey patch for reloading constants before hitting metal
# applications. More details in the introduction article at:
#
#   http://roman.flucti.com/reloading-rails-metal-applications
#

Rails::Rack::Metal.class_eval do
  # Prevent Metal from further require'ing source files, in order to let
  # AS::Dependencies handle constants.
  class << self
    def require(*args)
    end
  end

  # Remove already loaded metal constants so that they get loaded by
  # AS::Dependencies the next time they are needed.
  metals.grep(Module).each do |mod|
    $".delete(mod.name.underscore + ".rb")
    ActiveSupport::Dependencies.remove_constant(mod.name)
  end

  # Force metal constants to be reloaded before each request.
  def call_with_reload(*args, &block)
    @metals.clear
    RELOADER.reload do
      self.class.metals.each { |app| @metals[app] = true }
      call_without_reload(*args, &block)
    end
  end
  alias_method_chain :call, 'reload'
  
  # Expose the reloading mechanism via a stripped down Dispatcher instance.
  bare_dispatcher = Class.new(ActionController::Dispatcher) do
    def initialize
    end
    
    def reload
      reload_application
      begin
        yield
      ensure
        cleanup_application if respond_to? :cleanup_application
      end
    end
  end
  RELOADER = bare_dispatcher.new
end if Rails.env.development?