scope and an instance method

Question

I have a model

class User < ActiveRecord::Base
  has_many :articles

  def good_publisher?
    self.articles.size > 50
  end

  scope :good_publishers, -> where { ...???? }
end

How do I express the scope through good_publisher?? Something like

scope :good_publishers, -> where { x.good_publisher? }

What did you mean by express the scope through good_publisher? method? — Surya
– Surya, Commented Dec 31, 2014 at 11:39
@Surya, I mean, use user.good_publisher? in -> where { .... } — Incerteza
– Incerteza, Commented Dec 31, 2014 at 11:41
good_publisher? is an instance method, while a scope creates class method, so no... there's no way you can use instance method in a scope. What are you trying to do? — Surya
– Surya, Commented Dec 31, 2014 at 11:43
@Surya, calculate the total number of the "good_publishers". — Incerteza
– Incerteza, Commented Dec 31, 2014 at 11:50
No, I meant what are you planning to do with this scope? i.e. what are you intending to do with User. good_publishers and user.good_publisher? ? — Surya
– Surya, Commented Dec 31, 2014 at 12:03

Maurício Linhares · Accepted Answer · 2014-12-31 11:58:42Z

2

The scope has to be a SQL statement, your best bet here is to use a counter cache for the association.

At the Article class, include this:

belongs_to :user, counter_cache: true # you should already have this belongs_to, all that needs to happen is include the counter_cache

Then, create a migration that includes the articles_count field to user:

add_column :users, :articles_count

Once you have this, the scope can be written as:

scope :good_publishers, where("articles_count > 50")

answered Dec 31, 2014 at 11:58

Maurício Linhares

40.4k15 gold badges127 silver badges160 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

scope and an instance method

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related