nested attributes example

gistfile1.rb

class ExamResult
  has_many :answers, :dependent => :destroy
  accepts_nested_attributes_for :answers

  # for cleaner API
  alias_method :user_answers=, :answers_attributes=
end

class Answer
  belongs_to :exam_result
  belongs_to :question

  before_save :check_answer

  def correct_answer_given?
    question.correct_answer == user_answer
  end

  def check_answer
    self.correct = correct_answer_given?  

    true # return true so that it doesn't disrupt the after_save callback chain
  end
end

exam_result = ExamResult.new(:user_answers=>[{:user_answer=>"A",:question_id=>1},{:user_answer=>"B",:question_id=>2}])
exam_result.save # will create answer objects as well