Touch plugin for MongoMapper

gistfile1.rb

# encoding: UTF-8
module MongoMapper
  module Plugins
    module Touch
      extend ActiveSupport::Concern

      module InstanceMethods
        def touch(key = :updated_at) 
          raise "InvalidKey" unless self.key_names.include?(key.to_s) 
          self.set(key => Time.now.utc)

          true
        end 
      end
    end
  end
end

It's the first attempt to make the touchmethod (from ActiveRecord) available in Mongo documents.

The idea is to be able to update a Document's date field without updating the whole Document, without any validations or callbacks, … just like in ActiveRecord.

I don't know if it's the best way to do this, but right now it's dead simple and it works with a first level key.

the "setter" doesn't work if the key doesn't exist yet

Thanks to Kevin Lawver from the MongoMapper Google Group (http://groups.google.com/group/mongomapper/browse_thread/thread/62faeebcb0584f47) we can do this without using the driver, but the set method of MongoMapper's API.

But I prefer to store Dates/Times in UTC