has_and_belongs_to_many and after_save problem

I've got two models

class Payment < ActiveRecord::Base
  has_and_belongs_to_many :invoices

  after_save :update_invoices_state

  def update_invoices_state
    self.invoices.each{|i| i.update_state }
  end
end

class Invoice < ActiveRecord::Base
  has_and_belongs_to_many :payments

  def pending_value
    paid_value = Money.new(0,self.currency)
    self.payments.each{|payment| paid_value += payment.value}
    self.value - pa开发者_Python百科id_value
  end

  def update_state
    if self.pending_value.cents >= 0
      if self.due_on >= Time.zone.today
        new_state = :past_due_date
      else
        new_state = :pending
      end
    else
      new_state = :paid
    end
    self.update_attribute :state, new_state
  end
end

I've been debuggin this and I've found that when invoice.update_state is run self.payments is empty. Looks like HABTM hasn't been updated yet.

How could i solve this?

I believe HABTM has been mostly replaced by has_many :through.

You would create a join model, something like "InvoicePayment" (or something else creative)

class Payment < ActiveRecord::Base
    has_many :invoice_payments
    has_many :invoices, :through => :invoicepayments
end

class InvoicePayment < ActiveRecord::Base
    belongs_to :invoice
    belongs_to :payment
end

class Invoice < ActiveRecord::Base
    has_many :invoice_payments
    has_many :payments, :through => :invoice_payments 
end

This should fix your problem.