gistfile1.txt

class IndividualsController < ApplicationController
   def update
    @individual = Individual.find(params[:id])

    # When I tried to implement this as a callback I kept getting 'SystemStackError (stack level too deep)'
    #@individual.untrain

    if @individual.update_attributes(params[:individual])
      flash[:success] = "Individual was updated"
      redirect_to individuals_url
    else
      flash[:failure] = "Individual was NOT updated"
      render 'edit'
    end
  end
end

class Individual < ActiveRecord::Base

  #after_update :untrain

  validates :height, :presence => true, :numericality => true
  validates :weight, :presence => true, :numericality => true
  validates :gender, :presence => true

  MALE = 'Male'
  FEMALE = 'Female'

  MALEPROB = 0.5
  FEMALEPROB = 0.5

  GENDERS = [ MALE, FEMALE ]

  scope :untrained, Individual.where( :trained => false )
  scope :gender, lambda { |gender| where("gender = ?", gender ) }

  #private

  def untrain
    self.update_attributes( :trained => false )
  end
end