Rails 4 concern errors

Question

I've notice the new features of concern in rails4, and I read the document of it in http://edgeapi.rubyonrails.org/classes/ActiveSupport/Concern.html. But it seems doesn't work as I expect. Here is my code of my /models/concerns/current_user.rb.

require 'active_support/concern'

module CurrentUser
  extend ActiveSupport::Concern

  module ClassMethods
    def accessor_current_user
      attr_accessor :current_user
    end
  end

end

class ActiveRecord::Base
  include CurrentUser
end

You probably notice that last 3 lines of my code, that's because I want all my models can call the method and I think it may be a good way to achieve that. But when i start rails server, it just cannot call the accessor_current_user method. So I am confusing about this. I really don't know the reason. Hope someone can help me. :)

Update! Finally, i found it's maybe a good way to create a ActiveRecord::Base class in the initializers fold, and then include the CurrentUser in the class.

Pierre-Louis Gottfrois · Accepted Answer · 2013-08-13 12:45:16Z

1

Try:

require 'active_support/concern'

module CurrentUser
  extend ActiveSupport::Concern

  included do
    attr_accessor :current_user
  end

  module ClassMethods
  end

end

class ActiveRecord::Base
  include CurrentUser
end

Then you should be able to do something like this:

foo = Foo.new
foo.current_user

Where Foo is:

class Foo < ActiveRecord:Base
  include CurrentUser
end

edited Aug 13, 2013 at 12:45

answered Aug 13, 2013 at 10:50

Pierre-Louis Gottfrois

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4 Comments

hsming Over a year ago

Thanks for your answer, can you explain this? I tried to add the last 2 lines but still can't work.

Pierre-Louis Gottfrois Over a year ago

The last 2 lines are only here to illustrate. You should not add them. The basic ideas is to add an attr_accessor on any class that include your CurrentUser module. This is done with the included block.

hsming Over a year ago

Well, I know if I add include CurrentUser in the Foo class can work well, but that isn't what i want. Suppose you have 8 models need to call the accessor_current_user method, so in your way you need to add include CurrentUser in all the 8 models, i don't think it's best way. So i am wondering if i can write some code to achieve that goal.

Pierre-Louis Gottfrois Over a year ago

Including your CurrentUser module for every ActiveRecord::Base sub classes is not a good idea.

Neeraj Kumar · Accepted Answer · 2014-12-24 12:24:33Z

0

The way you are calling accessor_current_user is wrong. This way you can call ActiveRecord::Base.accessor_current_user method and it will execute the code without any error. And then you can call

ar = ActiveRecord::Base.new
ar.current_user = "foo"
ar.current_user # this will return 'foo'

But the correct way to implement the attr_accessor using ActiveSupport::Concern is

module CurrentUser
  extend ActiveSupport::Concern

  included do
    attr_accessor :current_user
  end

end

If you are writing your code in rails, then you don't need require 'active_support/concern'. Please refer http://blog.neerajk.com/articles/2014-11-26-is-active-support-concern-really-another-concern/

answered Dec 24, 2014 at 12:24

Neeraj Kumar

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