callback issue

byebug.rb

InvoicePayment.create()
byebug =>
  invoice_payments.size => 1
(byebug) id => 2861
(byebug) Invoice.find(2861).invoice_payments.size => 2

model.rb

class InvoicePayment < ActiveRecord::Base
 belongs_to :invoice
 after_save :{invoice.update_payment}
end

class Invoice < ActiveRecord::Base

  def checkpayments
    byebug => see console
    invoice_payments.map(&:amount).sum - price == 0
  end
end