Association using :inverse_of option.

inverse_of_example.rb

class Company < ActiveRecord::Base
  has_many :users, :inverse_of => :company
end

class User < ActiveRecord::Base
  belongs_to :company, :inverse_of => :users
end

# Code from the Consle

# irb(main):001:0> u = User.last
#   User Load (0.9ms)  SELECT "users".* FROM "users" ORDER BY "users"."id" DESC LIMIT 1
# => #<User id: 123, first_name: "Melissa", created_at: "2013-01-11 06:37:19", updated_at: "2013-01-11 06:37:19", password_digest: "$2a$10$iAa.v2FPD7DqnwZEvQrr2.RNwVG/wSJBTfO66YfosDou...", remember_token: "QbE7RM4xeBmeky2kVv7KxQ", admin: nil, last_name: "Post", title: "Co-Founder", frequency: 1, address_id: 141, company_id: 62, password_reset_sent_at: nil, password_reset_token: nil, linkedin_profile: "www.linkedin.com/", invitation_id: nil, invitation_limit: 5, birthdate: "1981-04-06", own_industry_id: 377, objective: ["1", "7"], day_preference: 4, time_zone: "Eastern Time (US & Canada)", avatar_file_name: nil, avatar_content_type: nil, avatar_file_size: nil, avatar_updated_at: nil, status: 2>

# irb(main):002:0> c = Company.find(62)
#   Company Load (7.7ms)  SELECT "companies".* FROM "companies" WHERE "companies"."id" = $1 LIMIT 1  [["id", 62]]
# => #<Company id: 62, name: "Vandelay Industries", created_at: "2013-01-11 05:07:45", updated_at: "2013-01-11 05:07:45">

# irb(main):003:0> c.users.count 
#    (0.5ms)  SELECT COUNT(*) FROM "users" WHERE "users"."company_id" = 62
# => 1

# irb(main):004:0> u.first_name == c.users.first.first_name
#   User Load (0.7ms)  SELECT "users".* FROM "users" WHERE "users"."company_id" = 62 LIMIT 1
# => true

# irb(main):005:0> u.first_name = "New Name"
# => "New Name"

# irb(main):006:0> u.first_name == c.users.first.first_name
#   User Load (0.7ms)  SELECT "users".* FROM "users" WHERE "users"."company_id" = 62 LIMIT 1
# => false

# I think I understand why this returns false (it's retrieving a new instance of c's first user from the db,
# which has yet to be updated), but based on the following documentationf from the Rails Guide below, I 
# would have expected it to reference the instance with the updated name

# From the guide http://guides.rubyonrails.org/association_basics.html
class Customer < ActiveRecord::Base
  has_many :orders, :inverse_of => :customer
end
 
class Order < ActiveRecord::Base
  belongs_to :customer, :inverse_of => :orders
end

c = Customer.first
o = c.orders.first
c.first_name == o.customer.first_name # => true
c.first_name = 'Manny'
c.first_name == o.customer.first_name # => true