how to build a record with multiple references with has many association in rails

I have 3 models named Article, User, Comment

class Article < ActiveRecord::Base
  has_many :comments
end

class User < ActiveRecord::Base
  has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :user
  belongs_to :article
end

Now, if I want to build a comment for an article, I can use

@comment = @article.comments.build(comment_params)

this will add article_id to the comment object

Now, if I want to add the user_id to object, I can add in the following way

@comment.user_id = current_user.id

But, if I want to auto populate user_id like article_id, what way I can do?