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Does inverse_of work with has_many?

When I use has_one, it works fine, but not on has_many. Here you can see that object_id is different from another because it runs another SQL to get it.

ruby-1.9.2-p290 :001 > e = Employee.create(name: 'rafael', active: false)
ruby-1.9.2-p290 :002 > b = Badge.create(number: 1, employee: e)
ruby-1.9.2-p290 :003 > a = Address.create(street: "123 Market St", city: "San Diego", employee: e)
ruby-1.9.2-p290 :004 > e = Employee.first
  Employee Load (0.2ms)  SELECT "employees".* FROM "employees" LIMIT 1
 => #<Employee id: 1, name: "rafael", active: false, created_at: "2011-10-04 17:09:25", updated_at: "2011-10-04 17:09:25"> 
ruby-1.9.2-p290 :002 > e.is_active?
 => false 
ruby-1.9.2-p290 :003 > e.object_id
 => 2182895380 
ruby-1.9.2-p290 :004 > e.badge.employee.is_active?
  Badge Load (17.6ms)  SELECT "badges".* FROM "badges" WHERE "badges"."employee_id" = 1 LIMIT 1
 => false 
ruby-1.9.2-p290 :005 > e.badge.employee.object_id
 => 2182895380 
ruby-1.9.2-p290 :006 > e.addresses.first.employee.is_active?
  Address Load (0.2ms)  SELECT "addresses".* FROM "addresses" WHERE "addresses"."employee_id" = 1 LIMIT 1
  Employee Load (0.3ms)  SELECT "employees".* FROM "employees" WHERE "employees"."id" = 1 LIMIT 1
 => false 
ruby-1.9.2-p290 :007 > e.addresses.first.employee.object_id
  Address Load (0.3ms)  SELECT "addresses".* FROM "addresses" WHERE "addresses"."employee_id" = 1 LIMIT 1
  Employee Load (0.2ms)  SELECT "employees".* FROM "employees" WHERE "employees"."id" = 1 LIMIT 1
 => 2181302220 
ruby-1.9.2-p290 :008 >

Here is the code I used to configure my test:

class Employee < ActiveRecord::Base
  has_many :addresses, :inverse_of => :employee
  has_one :badge, :inverse_of => :employee

  accepts_nested_attributes_for :addresses
  accepts_nested_attributes_for :badge
  # validates_associated :addresses

  def is_active?
    active
  end
end

class Address < ActiveRecord::Base
  belongs_to :employee, :inverse_of => :addresses

  validates :city, length: { within: 100..1000, message: "Too short"}, :if => lambda {|a| a.employee.is_active?}
end

class Badge < ActiveRecord::Base
  belongs_to :employee, :inverse_of => :badge

  validates :number, length: { within: 2..10, message: "Too long"}, :if => lambda {|b| b.employee.is_active?}
end
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3 answers

Yes Yes! Please refer to the “Bidirectional Associations” section of the Active Record Association API documents here: http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html

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No, it is not. According to the Rails Guide ,

  • : .
  • : .
  • : .
  • belongs_to has_many.
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The last part of this video on setting up Rails 5 models shows an example of how the has_many relationship behaves without and then with inverse_of. The RSpec test is written to confirm that object_ids are actually the same:

https://www.youtube.com/watch?v=5sfufoY59Ek&feature=youtu.be&t=42m54s

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