scope-madness.rb

# build scopes for owners, producers, and viewers.  each scope can be used
# with one, or more, users.  for example:
#
# Organization.with_owners(jane, john)
#
  {
    :owner => %w'owner',
    :producer => %w'owner producer',
    :viewer => %w'owner producer viewer'
  }.each do |name, roles|

    scope_name = "with_#{ name }".pluralize

    scope(scope_name, proc{ |*users|
      ids = list_of_ids(users)
      criteria = ids.map do |id|
        {'memberships' => {'$elemMatch' => {'user_id' => id, 'roles' => {'$in' => roles}}}}
      end
      Organization.where('$and' => criteria)
    })

    (class << self; self; end).module_eval do
      alias_method(scope_name.singularize, scope_name.pluralize)
    end

  end