scope in relationship

[grentis]

Hi all, 

is it possible to use scope in model relationships?

example

class Post < ActiveRecord::Base

  scope :published, where(:published, true) 

end

 

class User < ActiveRecord::Base 

  has_many :posts 

  has_many :published_posts, class_name: 'Post' ..... here I would like to use the same conditions of scope published without rewrite them

I know that I can write a method in User class instead of the has_many relationship, something like

def published_post 

  return self.posts.published  

end

but in this way I can't use the include: in the to_json method

@user.to_json(include: :published_posts)

and I can't use method: instead beacuse I have to use also the only: attribute to filter the attributes in the json output

Thanks to all