Rails custom validator cannot access new associated collection values

Question

I'm trying to write a custom validator to check that the 'Values' added to my 'Report' sum to a specific value (600) per category (behavior). My code follows:

Report:

class Report < ActiveRecord::Base
  attr_accessible :value_ids, :values_attributes
  accepts_nested_attributes_for :values

  validate :validates_behaviour_sums

  def values_by_behaviour
    hash_hash = Hash.new( 0 ) 
    values.each do |v|
      au_hash = hash_hash[ v.behaviour ] 
        if au_hash.nil
        au_hash = Hash.new( 0 )
      end
      au_hash.store( v.assessed_user, v )
      hash_hash.store( v.behaviour, au_hash )
    end
  end


  def validates_behaviour_sums
    sums_valid = true
    self.values_by_behaviour.each do |behaviour_values|
      unless behaviour_values.values.sum == 600
        sums_valid = false
      end
    end
    unless sums_valid
      errors.add(:values, "The behaviours in each category must equal 600." )
    end
  end
end

Value:

class Value < ActiveRecord::Base
  attr_accessible :value, :assessed_user_id, :behaviour_id

  belongs_to :assessed_user, :class_name => "User"
  belongs_to :behaviour

  belongs_to :report

  validates :value, :assessed_user_id, :behaviour_id, :presence => true
end

When I try to run this code, I get the following error:

NoMethodError in ReportsController#create

undefined method `nil' for 0:Fixnum

Rails.root: /Users/micah/dev/rails_projects/s2

Application Trace

app/models/report.rb:23:in `block in values_by_behaviour'
app/models/report.rb:18:in `values_by_behaviour'
app/models/report.rb:45:in `validates_behaviour_sums'
app/controllers/reports_controller.rb:35:in `create'

It appears that the collection, 'values' has not yet been set, but I don't know how else to validate them. It does accept the values and set them properly.

Answer 1

your current mistake is undefined method nil for 0:Fixnum. If you are checking for nil you should write au_hash.nil? instead of au_hash.nil, or if you want to check for zero you should use au_hash.zero?