Ruby on Rails-在before_save之前获取polymorphic_id

Question

I have a two models:

Polymorphic

class Custo < ActiveRecord::Base
  belongs_to :custavel, polymorphic: true
  accepts_nested_attributes_for :custavel, allow_destroy: true
  validates_presence_of :numero, :serie
  validates_uniqueness_of :numero, scope: :serie
end

Another class

class Pagamento < ActiveRecord::Base
  has_one :custo, as: :custavel
end

In general numero and serie are filled by user input, but only when the polymorphic is a Pagamento i need to fill the column numero with custavel_id .

Then, i tried it:

before_save :set_numero
def set_numero
  return unless custavel_type == 'Pagamento'
  write_attribute(:numero, custavel_id)
end

But it fails on validation because custavel_id doesn't exists yet. How to do it?

Answer 1

Modify the callback method

before_save :set_numero

def set_numero
  write_attribute(:numero, custavel_id) if custavel_type == 'Pagamento'
end