Return default value if you have nil value for the column

default_attribute_value.rb

module Extensions
  module DefaultAttributeValue
    def self.included(base)
      base.send :extend, ClassMethods
    end

    module ClassMethods
      def default_attribute_value(key, value)
        self.class_eval %Q{
          def #{key}
            value = read_attribute(:#{key})

            value || #{value}
          end
        }
      end
    end
  end
end

default_attribute_value_spec.rb

require 'spec_helper'

class TestClass
  include Extensions::DefaultAttributeValue

  attr_accessor :key

  default_attribute_value :key, 0

  def read_attribute(key)
    instance_variable_get("@#{key}")
  end
end

describe Extensions::DefaultAttributeValue do
  let(:object) { TestClass.new }

  it { object.key.should == 0 }

  context 'when key assigned' do
    before { object.key = 1 }

    it { object.key.should == 1 }
  end
end

stat.rb

class Stat < ActiveRecord::Base
  include Extensions::DefaultAttributeValue

  default_attribute_value :clicks, 0
end