Rails 3 controller - if question record doesn't have a corresponding answer record, create one

I've worked with rails 2... but i'm still a rails 3 noob/disaster.

@questions is a set of questions from the questions table. I need to make sure that each question has a corresponding answer record in the answers table. If one does not exist, i need to create one with the default value of zero. In my controller i have the following:

# create records for answers that do not exist yet
@questions.each do |q|
  a = Answer.where(q.id = Answer.question_id and current_user.id = Answer.user_id )
  if a.nil?
    Answer.new(:question_id => q.id, :score => 0)
  end
end

I am getting this error:

undefined method `question_id'

I'm going on vacation and taking the 4th edition of Agile Web Development with Rails (don't tell my wife :=]) Any help you can offer here would help.

Thanks.

Your code should look like this

@questions.each do |q|
  a = Answer.where(:question_id => q.id, :user_id => current_user.id)
  if a.empty?
    Answer.new(:question_id => q.id, :score => 0)
  end
end

But it can be refactored as

@questions.each do |q|
  q.answers.create(:score => 0) unless q.answers.where(:user => current_user).any?
end

EDIT

As far as you don't understand what is going on here: you should or create or save your object:

answer = Answer.new(:question_id => q.id, :score => 0)
answer.save

or

Answer.create(:question_id => q.id, :score => 0)

The activerecord query syntax is incorrect. It should be something like this -

@questions.each do |q|
  a = Answer.where("question_id = ? AND user_id = ?", q.id, current_user.id )
  if a.nil?
    Answer.new(:question_id => q.id, :score => 0)
  end
end

Look at this post for more details http://m.onkey.org/active-record-query-interface

assuming you have added a has_many relationship to Question, you could do this

@questions.each do |q|
  if q.answers.empty?
    q.answers.create! :score => 0, :user => current_user
  end
end

It iterates over the questions, checks to see if the question has answers, and adds one with score zero and user current_user, if it is empty. It also will raise an error if the save fails (that's what adding ! to create or save does).

You will have to ensure your models know about the relationships for this to work:

class Question < ActiveRecord::Base
  has_many :answers
end

class Answer < ActiveRecord::Base
  belongs_to :question
  belongs_to :user
end