application_controller.rb

class ApplicationController < ActionController::Base

  before_filter :fetch_authors_and_categories

  #...

  private

  def fetch_authors_and_categories
    Couch.client(:bucket => 'system').pipelined do
      @authors = Author.popular
      @categories = Category.popular
    end
  end

  #...

end

author.rb

class Author < Couchbase::Model

  #...

  def self.popular(limit=8)
    begin
      contribs = Couch.client(:bucket => 'system').get("contributors")["data"]
      return contribs.map! { |contrib| new (contrib) }
    rescue Couchbase::Error::NotFound
      #...
      return []
    end
  end

end

couch.rb

module Couch

  class << self

    def url
      ENV['COUCHBASE_URL'] || "http://127.0.0.1:8091/pools/default"
    end

    def client(options = {})
      bucket = options.delete(:bucket) || "default"
      @clients ||= {}
      @clients[bucket] ||= Couchbase.new(url, :bucket => bucket)
    end

  end

end

Couch.client(:bucket => 'system').run do
  Author.popular.load {|res| @authors = res.collection}
  Category.popular.load {|res| @categories = res.collection}
end

Where #load is the same as #fetch but yield whole collection at once

It should work right now with

@articles = []
Couch.client(:bucket => 'system').run do
  Article.popular.fetch{|doc| @articles << doc}
end