How can I achieve a functionality similar to "auto-insertion of timestamps"

I have a couple o开发者_如何学JAVAf fields created_by and updated_by in most of my tables. This would contain the user id of the user who created or updated the Object. is it possible to have a similar function like how rails handles created_at? I basically want it to function the same way as the timestamps insertion. I should be able to define in the columns in the migration script and configure rails to fetch the user object from a helper method everytime when it changes the particular object. Is there a direct way to do it or is there a plugin which does this?

Also you can do this without gems but with Rails Observers

You can create observer like this:

class UserTouchObserver < ActiveRecord::Observer
  observe :product, :post, :comment

  def after_create(model)
    update_attribute(:created_by, current_user.id) if model.respond_to?(:created_by)
  end

  def after_update(model)
    update_attribute(:updated_by, current_user.id) if model.respond_to?(:updated_by)
  end
end

I was able to find a few plugins on github that do just this:

• https://github.com/jnunemaker/user_stamp
• https://github.com/bokmann/userstamp_basic