ActiveRecord::MissingAttributeError (can't write unknown attribute) in Rails

Question

I want to create a new "AnswerStat" object and save it in the database. I am getting:

can't write unknown attribute `answer_stat_id'

app/models/answer_stat.rb:14:in `new'
app/models/answer_stat.rb:14:in `add_answer'
app/controllers/users_controller.rb:31:in `block in index'
app/controllers/users_controller.rb:30:in `each'

answer_stat_id does not exist, it refers I guess to the primary key of the table answer_stats which is id. I do not explicitly declare this attribute of course. Why is Rails looking for this inexistent attribute? Code:

class AnswerStat < ActiveRecord::Base

  attr_accessible :contact, :statement, :answer_sum, :answer_count, :variation

  belongs_to :contact, :class_name => "Friend"
  has_one :statement

  validates_uniqueness_of :contact, :scope => :statement

  def self.add_answer(answer)
    if stat = AnswerStat.find_by_contact_id_and_statement_id(answer.contact.id, answer.statement.id)
    ...........do some stuff...........
    else
      @answer_stat = AnswerStat.new(:contact => answer.contact, :statement => answer.statement, :answer_count => 1, :answer_sum => answer.description, :variation => answer.description)
      @answer_stat.save
    end      
  end

I am calling it from the rails console, or from any controller, using:

   Answer.all.each do |a|
      AnswerStat.add_answer(a)
   end

The answer_stats table (sqlite3 using PRAGME table_info(answer_stats)):

0|id|INTEGER|1||1
1|contact_id|integer|0||0
2|answer_sum|integer|0||0
3|answer_count|integer|0||0
4|created_at|datetime|1||0
5|updated_at|datetime|1||0
6|statement_id|integer|0||0
7|variation|integer|0||0

Thanks in advance

Answer 1

it could come from the statement attribute, which refers to an associated model.I think it's looking for an answer_stat_id foreign key in the statements table.

You should either :

• create the associated answer via @answer_stat.build_statement(...)
• redesign your model associations if the statement is meant to preexist the stat