simple_transactional_persistence_with_pstore.rb

require "pstore"

module Notes
  class << self
    attr_accessor :store_location

    def put_note(id, note)
      store.transaction do
        store[:notes] ||= {}
        store[:notes][id] = note
      end
    end

    def delete_note(id)
      store.transaction do
        store[:notes] ||= {}
        store[:notes].delete(id)
      end
    end

    def notes
      store.transaction do
        store[:notes] ||= {}
      end
    end

    def clear_notes
      store.transaction do
        store[:notes] = {}
      end
    end

    private

    def store
      @store ||= begin
        raise "Notes store location is not defined" unless store_location
        PStore.new(store_location)
      end
    end
  end
end

Notes.store_location = "notes.pstore"

Notes.notes                   #=> {}
Notes.put_note(1, "fooman")   #=> "fooman"
Notes.put_note(2, "barbaz")   #=> "barbaz"
Notes.notes                   #=> {1=>"fooman", 2=>"barbaz"}
Notes.delete_note(1)          #=> "fooman" 
Notes.notes[2]                #=> "barbaz"