inverse_of与has_many一起使用吗？

Question

当我使用has_one时它可以很好地工作,但不能在has_many上工作.在这里你可以看到object_id是不同的,因为它运行另一个SQL来再次获取它.

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 >

这是我用来设置测试的代码:

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

Answer 1

不,不是.根据Rails指南,

• 它们不适用于:通过协会.
• 它们不兼容:多态关联.
• 它们不适用于:作为协会.
• 对于belongs_to关联,忽略has_many反向关联.

Answer 2

是的，它确实！请在此处参考 Active Record 中关联的 API 文档的双向关联部分：http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html