ruby 30 lines · 9 steps

How scopes compose in Rails

A single Article model uses scopes, default_scope, and class methods that chain into composable, reusable queries.

Explained by highlit
Rails Intermediate scopes query-composition activerecord soft-delete chaining
1class Article < ApplicationRecord
2 belongs_to :author
3 
4 default_scope { where(deleted_at: nil) }
5 
6 scope :published, -> { where(published: true) }
7 scope :draft, -> { where(published: false) }
8 scope :recent, -> { order(created_at: :desc) }
9 scope :by_author, ->(author) { where(author: author) }
10 scope :published_since, ->(date) { published.where("published_at >= ?", date) }
11 
12 scope :popular, -> { where("view_count >= ?", 1_000).recent }
13 
14 scope :search, ->(term) {
15 return all if term.blank?
16 where("title ILIKE :q OR body ILIKE :q", q: "%#{term}%")
17 }
18 
19 scope :with_comments, -> {
20 joins(:comments).distinct
21 }
22 
23 def self.archived
24 unscope(where: :deleted_at).where.not(deleted_at: nil)
25 end
26 
27 def self.trending(limit = 10)
28 published.popular.limit(limit)
29 end
30end
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Scopes are just chainable methods returning relations, so they compose freely into larger queries.
  2. 2default_scope silently filters every query, which is powerful but easy to forget — unscope when you need to escape it.
  3. 3Class methods and scopes are interchangeable for building queries, letting you mix lambdas with conditional Ruby logic.

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