accepts_nested_attributes_for wrong number of arguments (1 for 0)

I have a problem with has_many relationship and nested attributes

class WorkOrder < ActiveRecord::Base   has_many :services,:order=> :row,:dependent => :destroy   belongs_to :car   belongs_to :company   belongs_to :service_offer   belongs_to :user_rank, :class_name => 'Rank',:foreign_key => 'user_rank_id'   belongs_to :company_rank,:class_name =>'Rank', :foreign_key => 'company_rank_id

  accepts_nested_attributes_for :services .... end

class Service < ActiveRecord::Base   has_many :material_services, :order =>:row   belongs_to :service_type   belongs_to :work_order   acts_as_list :scope=> "work_order_id",:column=>:row   has_and_belongs_to_many :tasks   attr :rows_id,true

  accepts_nested_attributes_for :material_services


class MaterialService < ActiveRecord::Base   belongs_to :service   acts_as_list :scope=> "service_id" ,:column=>:row   belongs_to :material_service_type

  accepts_nested_attributes_for :material_service_type


I have WorkOrder that has_many Services and Services has_many MaterialServices...but I get an error when try to create a services through WorkOrder

wo = that throw wrong number of arguments (1 for 0)

but if I run s = ms = That works perfect... I tried to debug the ActiveRercord but was imposible for me :slight_smile: I just can't see what I have different between WorkOrder and Service relationship and Service and MaterialServices.

Any help is very usefull