---
title: "Rails 5 makes belongs_to association required by default"
description:
  "Rails 5 makes it necessary to have belongs_to association record by default."
canonical_url: "https://www.bigbinary.com/blog/rails-5-makes-belong-to-association-required-by-default"
markdown_url: "https://www.bigbinary.com/blog/rails-5-makes-belong-to-association-required-by-default.md"
---

# Rails 5 makes belongs_to association required by default

Rails 5 makes it necessary to have belongs_to association record by default.

- Author: Abhishek Jain
- Published: February 15, 2016
- Categories: Rails 5, Rails

In Rails 5, whenever we define a `belongs_to` association, it is required to
have the associated record present by default after
[this](https://github.com/rails/rails/pull/18937) change.

It triggers validation error if associated record is not present.

```ruby

class User < ApplicationRecord
end

class Post < ApplicationRecord
  belongs_to :user
end

post = Post.create(title: 'Hi')
=> <Post id: nil, title: "Hi", user_id: nil, created_at: nil, updated_at: nil>

post.errors.full_messages.to_sentence
=> "User must exist"

```

As we can see, we can't create any `post` record without having an associated
`user` record.

## How to achieve this behavior before Rails 5

In Rails 4.x world To add validation on `belongs_to` association, we need to add
option `required: true` .

```ruby

class User < ApplicationRecord
end

class Post < ApplicationRecord
  belongs_to :user, required: true
end

post = Post.create(title: 'Hi')
=> <Post id: nil, title: "Hi", user_id: nil, created_at: nil, updated_at: nil>

post.errors.full_messages.to_sentence
=> "User must exist"

```

By default, `required` option is set to `false`.

## Opting out of this default behavior in Rails 5

We can pass `optional: true` to the `belongs_to` association which would remove
this validation check.

```ruby

class Post < ApplicationRecord
  belongs_to :user, optional: true
end

post = Post.create(title: 'Hi')
=> <Post id: 2, title: "Hi", user_id: nil>

```

But, what if we do not need this behavior anywhere in our entire application and
not just a single model?

## Opting out of this default behavior for the entire application

New Rails 5 application comes with an initializer named
`new_framework_defaults.rb`.

When upgrading from older version of Rails to Rails 5, we can add this
initializer by running `bin/rails app:update` task.

This initializer has config named
`Rails.application.config.active_record.belongs_to_required_by_default = true`

For new Rails 5 application the value is set to `true` but for old applications,
this is set to `false` by default.

We can turn off this behavior by keeping the value to `false`.

```ruby

Rails.application.config.active_record.belongs_to_required_by_default = false

class Post < ApplicationRecord
  belongs_to :user
end

post = Post.create(title: 'Hi')
=> <Post id: 3, title: "Hi", user_id: nil, created_at: "2016-02-11 12:36:05", updated_at: "2016-02-11 12:36:05">

```

## Links

- [Human page](https://www.bigbinary.com/blog/rails-5-makes-belong-to-association-required-by-default)