rails--rails/lib/active_job/queue_adapter.rb

require 'active_job/queue_adapters/inline_adapter'
require 'active_support/core_ext/string/inflections'

module ActiveJob
  module QueueAdapter
    mattr_reader(:queue_adapter) { ActiveJob::QueueAdapters::InlineAdapter }

    def queue_adapter=(name_or_adapter)
      if name_or_adapter.is_a?(Symbol) || name_or_adapter.is_a?(String)
        adapter = load_adapter(name_or_adapter)
      else
        adapter = name_or_adapter
      end
      
      @@queue_adapter = adapter
    end

    private
      def load_adapter(name)
        require "active_job/queue_adapters/#{name}_adapter"
        "ActiveJob::QueueAdapters::#{name.to_s.camelize}Adapter".constantize
      end
  end
end