gistfile1.txt

class Account < ActiveRecord::Base
  scope :open, where(:closed => false)
end
class Group < ActiveRecord::Base
  has_many :accounts
end

=> Account.open
Account Load (0.6ms)  SELECT `accounts`.* FROM `accounts` WHERE `accounts`.`closed` = 0
=> []
=> g = Group.first
=> g.accounts.open
ArgumentError: wrong number of arguments (0 for 1)
from ~/.rbenv/versions/1.9.3-p392/lib/ruby/1.9.1/open-uri.rb:27:in `open'
from ~/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/activerecord-3.1.12/lib/active_record/associations/collection_proxy.rb:108:in `method_missing'