How to get the current_user in a model observer?

问题

Given the following models:

Room (id, title)
RoomMembers (id, room_id)
RoomFeed, also an observer

When a Room title is updated, I want to create a RoomFeed item, showing who the user is who made the update.

@room.update_attributes(:title => "This is my new title")

Problem is in my observer for RoomFeed:

def after_update(record)
   # record is the Room object
end

The is no way for me to get the user.id of the person who just made the update. How do I go about doing that? is there a better way to do the update so I get the current_user?

回答1:

I think what you are looking for is, room.updated_by inside your observer. If you don't want to persist the updated_by, just declare it as an attr_accessor. Before you push the update, make sure you assign the current_user to updated_by, may be from you controller.

回答2:

This is a typical "separation of concern" issue.

The current_user lives in the controller and the Room model should know nothing about it. Maybe a RoomManager model could take care of who's changing the name on the doors...

Meanwhile a quick & dirty solution would be to throw a (non persistant) attribute at Room.rb to handle the current_user....

# room.rb
class Room
  attr_accessor :room_tagger_id
end

and pass your current_user in the params when updating @room.

That way you've got the culprit! :

def after_update(record)
   # record is the Room object
   current_user = record.room_tagger_id
end

回答3:

Create the following

class ApplicationController
  before_filter :set_current_user

  private
  def set_current_user
    User.current_user = #however you get the current user in your controllers
  end
end

class User
   ...
   def self.current_user
     @@current_user
   end
   def self.current_user= c
     @@current_user = c
   end
   ...
end

Then use...

User.current_user wherever you need to know who is logged in.

Remember that the value isn't guaranteed to be set when your class is called from non-web requests, like rake tasks, so you should check for .nil?

回答4:

I guess this is a better approach

http://rails-bestpractices.com/posts/47-fetch-current-user-in-models

回答5:

Update user.rb

class User < ActiveRecord::Base
  cattr_accessor :current
end

Update application_controller.rb

class ApplicationController
  before_filter :set_current_user

  private
  def set_current_user
    User.current = current_user
  end
end

Then you can get logged user by User.current anywhere. I'm using this approach to access user exactly in observers.

来源：https://stackoverflow.com/questions/7181036/how-to-get-the-current-user-in-a-model-observer

标签

ruby-on-rails

ruby-on-rails-3

activerecord

observer-pattern