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has_one through associations not saved correctly

#3480

Summary

Attributes created using has_one :through associations are lost upon serialization to the database.

Details

class Club < ActiveRecord::Base
  has_one :membership
end

class Membership < ActiveRecord::Base
  belongs_to :person
  belongs_to :club
end

class Person < ActiveRecord::Base
  has_one :membership
  has_one :club, :through => :membership
end

require 'test_helper'

class PersonTest < ActiveSupport::TestCase
  test "person's club is saved" do
    p = Person.new
    c = Club.new
    p.club = c
    assert_equal c, p.club
    c.save!; c.reload
    p.save!; p.reload
    assert_equal c, p.club
  end
end

$ ruby -Itest test/unit/person_test.rb
Loaded suite test/unit/person_test
Started
F
Finished in 0.057744 seconds.

  1) Failure:
test_person's_club_is_saved(PersonTest) [test/unit/person_test.rb:11]:
<#<Club id: 1, created_at: "2009-11-11 01:01:47", updated_at: "2009-11-11 01:01:47">> expected but was
<nil>.

1 tests, 2 assertions, 1 failures, 0 errors

Reported by gerad · November 11th, 2009 @ 12:15 AM

Activity

gerad
Also happens on 2.3.4 version 7ba80252a5a6bd94c8445347caee663b12c1a526

November 11th, 2009 @ 01:03 AM
Jigar Patel
Three cases -
1. p = Person.new
c = Club.new p.club = c This line will insert a new row in memberships table with both person_id and club_id as nil.
c.save p.save Both objects will be saved without any related membership. Hence your test case fails.
1. p = Person.new
  c = Club.new c.save p.club = c
This will create an entry in Membership table with club_id = "c.id" and person_id as nil
p.save will save the object but without any related membership and hence without any related organization.
1. p = Person.new
  p.save p will be a Person with some id.
  c = Club.new c.save c will be a Club with some id.
  p.club = c This will create an entry in memberships table with person_id and club_id pointing to corresponding rows in persons and clubs tables.
  p.save will save and you will be able to fetch club.
July 24th, 2010 @ 12:58 PM

lakshmanan

I ran your testcase statements in console and I test Membership after every statement. You are not saving anything

In short -> you are playing in memory without saving anything. so literally you are playing with nils

>> p = Person.new
=> #<Person id: nil, created_at: nil, updated_at: nil>
>> Membership.last
=> nil
>> c = Club.new
=> #<Club id: nil, created_at: nil, updated_at: nil>
>> Membership.last
=> nil
>> p.club = c
=> #<Club id: nil, created_at: nil, updated_at: nil>
>> Membership.last
=> nil
>> c.save!
=> true
>> Membership.last
=> nil
>> c.reload
=> #<Club id: 2, created_at: "2010-07-24 11:57:24", updated_at: "2010-07-24 11:57:24">
>> p.save!

# after this statement - your test will pass

=> true
>> Membership.last
=> #<Membership id: 2, club_id: nil, person_id: 2, created_at: "2010-07-24 11:57:43", updated_at: "2010-07-24 11:57:43">

Hope it helps

July 24th, 2010 @ 01:08 PM

Rohit Arondekar
- State changed from new to invalid
- Importance changed from to Low
p.club and c are not the same. c is created when c is saved. While p.club is created when p is saved.

September 27th, 2010 @ 02:52 PM