sequel_add_associated_object_test_case.rb

require 'sequel'
require 'logger'

DB = Sequel.sqlite(loggers: [Logger.new(STDOUT)])

DB.create_table :authors do
  primary_key :id
  String :name
end

DB.create_table :books do
  primary_key :id
  foreign_key :author_id
  String :title
end

class Author < Sequel::Model
  one_to_many :books
end

class Book < Sequel::Model
  many_to_one :author
end

author = Author.create(name: 'Douglas Adams')

author.add_book(title: 'Hithikers guide to the galaxy')
puts author.associations[:books].inspect
# => nil

puts author.books.inspect
# I, [2018-10-31T11:39:43.254256 #18170]  INFO -- : (0.000090s) SELECT * FROM `books` WHERE (`books`.`author_id` = 1)
# => [#<Book @values={:id=>1, :author_id=>1, :title=>"Hithikers guide to the galaxy"}>]