pretty-urls-with-mongoid.rb

#
# NAME
#   Sequence
#
# SYNOPSIS
#   generate monotomically increasing but *pretty* ids in mongoid
#
# DESCRIPTION
#   mongo is sweet, but object_ids or uuids in urls are not.
#
#   following is a teeny bit of code which can be used to effectiently
#   generate batches of pretty integer type ids for your records and voila:
#   pretty urls.
#
# USAGE
#
#   class A
#     include Mongoid::Document
#
#     field(:_id, :default => proc{ Sequence[A].next })
#     identity(:type => String)
#
#   # this is just to make find mo-betta, mongoid doesn't cast arguments to
#   # find - it is not required
#   #
#     def A.find(*args, &block)
#       args[0] = args[0].to_s if args.size == 1
#       super
#     end
#   end
#
#   p Array.new(3){ A.create.id }           #=> [1,2,3]
#   p [1,2,3].map{|id| A.find(id).id}       #=> ["1","2","3"]
#   p ["1","2","3"].map{|id| A.find(id).id} #=> ["1","2","3"]
#


class Sequence
  include Mongoid::Document

  field(:name)

  field(:current, :default => 1)
  field(:step, :default => 10)

  validates_presence_of(:name)
  validates_uniqueness_of(:name)
  index(:name, :unique => true)

  Cache = Map.new

  class << Sequence
    def for(name)
      name = name.to_s

      Cache[name] ||= (
        begin
          create!(:name => name)
        rescue
          where(:name => name).first || create!(:name => name)
        end
      )
    end

    alias_method('[]', 'for')
  end

  def next
    if @value.nil? or @value == @last_value
      generate_next_values!
    end
    @value
  ensure
    @value += 1
  end

  def generate_next_values!
    @last_value = inc(:current, step)
    @value = @last_value - step
  end

  def reset!
    update_attributes!(:current => 1)
  ensure
    @value = @last_value = nil
  end
end

just for reference, this is multi-process safe, fast, and could easily be augmented for multi-node setups.

https://groups.google.com/forum/#!topic/mongoid/SAKmkVyA46o

This isn't a good idea because the value of an id is uniqueness; which UUIDs provide. It's not safe, for example, you couldn't merge dbs and assume uniquess based on your one sequenced attribute. Friendly URLs are a different matter.

Why not just use mongoid_slug?

+1 mongoid_slug