Overwriting ActiveRecord::Base.content_columns

Jan wrote:

I want to define my own Content_colums methode as part of the ActiveRecord::Base class.

To do so, I have added the following code:

require 'model_extensions'
ActiveRecord::Base.send(:extend, ModelExtensions)

module ModelExtensions
  #Define Mixins for the ActiveRecord::Base modelclass
  # Define list of available items for select
  def valid_items(current_item=nil)
    #.... works fine

  # Overwrite displayble columns attribute, eliminate: created_* and updated_*
  def content_columns
    @content_columns ||= columns.reject { |c| c.primary || c.name =~ /(_id|_count)$/ || c.name == inheritance_column || c.name == locking_column || c.name =~ /(created_|updated_)/}

However, this won't work for the content_columns! The valid_items method though works perfectly as it is added to the AR:Base class.
But overwriting content_columns has no effect at all.
I tried to put 'attr :content_columns, true' but no effect neither

extend will only add methods, not re-define existing ones.

Instead, just write model_extensions.rb as

class ActiveRecord::Base
   def self.valid_items(current_item=nil)

   def self.content_columns

and require this in environment.rb