Rails: has_many through: class_name: の習作 https://note.com/usutani/n/nb3d1fe9e085b

has_many__through__class_name.rb

# frozen_string_literal: true

# Rails: 私の好きなコード（5）永続化とロジックを絶妙にブレンドするActive Record（翻訳）
# https://techracho.bpsinc.jp/hachi8833/2023_04_18/127103
# Topic
#   has_many :blocked_trackers, through: :entries, class_name: "Entry::BlockedTracker"
#
# https://github.com/rails/rails/blob/main/guides/bug_report_templates/active_record_gem.rb
# Rename: Post(posts) => Topic(topics), Comment(comments) => Entry(entries)
# New: Entry::BlockedTracker(entry_blocked_trackers)

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  # Activate the gem you are reporting the issue against.
  gem "activerecord", "~> 7.0.0"
  gem "sqlite3"
end

require "active_record"
require "minitest/autorun"
require "logger"

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :topics, force: true do |t|
  end
  create_table :entries, force: true do |t|
    t.integer :topic_id
  end
  create_table :entry_blocked_trackers, force: true do |t|
    t.integer :entry_id
  end
end

class Topic < ActiveRecord::Base
  has_many :entries
  has_many :blocked_trackers, through: :entries, class_name: "Entry::BlockedTracker"
end
class Entry < ActiveRecord::Base
  belongs_to :topic
  has_many :blocked_trackers
end
class Entry::BlockedTracker < ActiveRecord::Base
  belongs_to :entry
end

class BugTest < Minitest::Test
  def test_association_stuff
    topic = Topic.create!
    entry = Entry.create!
    topic.entries << entry

    assert_equal 1, topic.entries.count
    assert_equal 1, Entry.count
    assert_equal topic.id, Entry.first.topic.id

    blocked_tracker = Entry::BlockedTracker.create!
    entry.blocked_trackers << blocked_tracker

    assert_equal 1, Entry::BlockedTracker.count
    assert_equal 1, topic.blocked_trackers.count
    assert_equal blocked_tracker.id, topic.blocked_trackers.first.id

    topic.entries << Entry.create!

    assert_equal 2, topic.entries.count
    assert_equal 2, Entry.count
    assert_equal 1, topic.blocked_trackers.count
    assert_equal blocked_tracker.id, topic.blocked_trackers.first.id
  end
end