Update counters monkey patch when an association get updated

active_record_extensions.rb

module FixUpdateCounters

  def fix_updated_counters
    self.changes.each {|key, value|
      # key should match /master_files_id/ or /bibls_id/
      # value should be an array ['old value', 'new value']
      if key =~ /_id/
        changed_class = key.sub(/_id/, '')

        # Get real class of changed attribute, so work both with namespaced/normal models
        klass = self.association(changed_class.to_sym).klass

        # Namespaced model return a slash, split it.
        unless (counter_name = "#{self.class.name.underscore.pluralize.split("/")[1]}_count".to_sym)
          counter_name = "#{self.class.name.underscore.pluralize}_count".to_sym
        end

        klass.decrement_counter(counter_name, value[0]) unless value[0] == nil
        klass.increment_counter(counter_name, value[1]) unless value[1] == nil
      end
    }
  end 
end

ActiveRecord::Base.send(:include, FixUpdateCounters)

model.rb

class (Namespaced::)Model < ActiveRecord::Base
  belongs_to :association, counter_cache: true

  after_update :fix_updated_counters
end