gistfile1.rb

# models/user.rb
class User < ActiveRecord::Base
  def self.current
    Thread.current[:user]
  end

  def self.current=(user)
    Thread.current[:user] = user
  end
end

#controllers/application_controller.rb
class ApplicationController < ActionController::Base
    def set_current_user
      User.current = current_user
    end
end

# in de controller van hond-ouder relaties in de actie waarin je de honden opslaat (update, create)
def update (en/of: def create)
  ...
  User.current = current_user
  ...
end

# models/dog.rb
before_save :set_user

def set_user
  self.user_id = User.current.id
end