Fetch current user in models

I don't remember how many times I need to fetch the current user in models, for example, I want to log who creates, updates or destroys a post in the Audit model. There is no default way to fetch the current user in models, current_user object is always assigned in controllers (thanks to authentication plugins, restful_authentication, authlogic and devise), we can pass the current user object from controllers to models, but it is too ugly. I think the better way is to add the current user to User model by Thread.current hash.

class User < ActiveRecord::Base
  def self.current
    Thread.current[:user]
  end
  def self.current=(user)
    Thread.current[:user] = user
  end
end

As you seen, we add two class methods to User model, User.current to fetch the current user and User.current= to assign the current user. So what you need to do is to assign the current user in User model every request you need a current user. Such as

class ApplicationController < ActionController::Base
    def set_current_user
      User.current = current_user
    end
end

class PostsController < ApplicationController
  before_filter :require_user # require_user will set the current_user in controllers
  before_filter :set_current_user
end

Now you can easily fetch the current_user in models by User.current, enjoy it!