---
title: "Rails 5 supports bi-directional destroy dependency"
description:
  "We can now add bi-directional destroy dependency on Rails associations"
canonical_url: "https://www.bigbinary.com/blog/Rails-5-supports-bi-directional-destroy-dependency"
markdown_url: "https://www.bigbinary.com/blog/Rails-5-supports-bi-directional-destroy-dependency.md"
---

# Rails 5 supports bi-directional destroy dependency

We can now add bi-directional destroy dependency on Rails associations

- Author: Abhishek Jain
- Published: May 12, 2016
- Categories: Rails 5, Rails

In Rails 4.x, it is not possible to have destroy dependency on both sides of a
bi-directional association between the two models as it would result in an
infinite callback loop causing `SystemStackError: stack level too deep`.

```ruby

class User < ActiveRecord::Base
  has_one :profile, dependent: :destroy
end

class Profile < ActiveRecord::Base
  belongs_to :user, dependent: :destroy
end

```

Calling `User#destroy` or `Profile#destroy` would lead to an infinite callback
loop.

```ruby

>> user = User.first
=> <User id: 4, name: "George">

>> user.profile
=> <Profile id: 4>

>> user.destroy
=> DELETE FROM `profiles` WHERE `profiles`.`id` = 4
   ROLLBACK
SystemStackError: stack level too deep

```

Rails 5
[supports bi-directional destroy dependency](https://github.com/rails/rails/pull/18548)
without triggering infinite callback loop.

```ruby

>> user = User.first
=> <User id: 4, name: "George">

>> user.profile
=> <Profile id: 4, about: 'Rails developer', works_at: 'ABC'>

>> user.destroy
=> DELETE FROM "profiles" WHERE "posts"."id" = ?  [["id", 4]]
   DELETE FROM "users" WHERE "users"."id" = ?  [["id", 4]]
=> <User id: 4, name: "George">

```

There are many instances like above where we need to destroy an association when
it is destroying itself, otherwise it may lead to orphan records.

This feature adds responsibility on developers to ensure adding destroy
dependency only when it is required as it can have unintended consequences as
shown below.

```ruby

class User < ApplicationRecord
  has_many :posts, dependent: :destroy
end

class Post < ApplicationRecord
  belongs_to :user, dependent: :destroy
end

>> user = User.first
=> <User id: 4, name: "George">

>> user.posts
=> <ActiveRecord::Associations::CollectionProxy [<Post id: 11, title: 'Ruby', user_id: 4>, #<Post id: 12, title: 'Rails', user_id: 4>]>
```

As we can see "user" has two posts. Now we will destroy first post.

```ruby
>> user.posts.first.destroy
=> DELETE FROM "posts" WHERE "posts"."id" = ?  [["id", 11]]
   SELECT "posts".* FROM "posts" WHERE "posts"."user_id" = ?  [["user_id", 4]]
   DELETE FROM "posts" WHERE "posts"."id" = ?  [["id", 12]]
   DELETE FROM "users" WHERE "users"."id" = ?  [["id", 4]]

```

As we can see, we wanted to remove post with id "11". However post with id "12"
also got deleted. Not only that but user record got deleted too.

In Rails 4.x this would have resulted in
`SystemStackError: stack level too deep` .

So we should use this option very carefully.

## Links

- [Human page](https://www.bigbinary.com/blog/Rails-5-supports-bi-directional-destroy-dependency)