---
title: "ApplicationRecord in Rails 5"
description:
  "If we want to add a functionality to all models we no longer need to pollute
  whole ActiveRecord::Base. Just add that feature to ApplicationRecord."
canonical_url: "https://www.bigbinary.com/blog/application-record-in-rails-5"
markdown_url: "https://www.bigbinary.com/blog/application-record-in-rails-5.md"
---

# ApplicationRecord in Rails 5

If we want to add a functionality to all models we no longer need to pollute
whole ActiveRecord::Base. Just add that feature to ApplicationRecord.

- Author: Prathamesh Sonpatki
- Published: December 28, 2015
- Categories: Rails 5, Rails

[Rails 5 beta-1](http://weblog.rubyonrails.org/2015/12/18/Rails-5-0-beta1/) was
recently released and one of the notable change was introduction of
[ApplicationRecord](https://github.com/rails/rails/pull/22567).

Up to Rails 4.2, all models inherited from `ActiveRecord::Base`. But starting
from Rails 5, all models will inherit from `ApplicationRecord`.

```ruby
class Post < ApplicationRecord
end
```

What happened to `ActiveRecord::Base` ?

Well not much changed in reality. Following file will be automatically added to
models in Rails 5 applications.

```ruby
# app/models/application_record.rb
class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true
end
```

This behavior is similar to how controllers inherit from `ApplicationController`
instead of inheriting from `ActionController::Base`.

Now `ApplicationRecord` will be a single point of entry for all the
customizations and extensions needed for an application, instead of monkey
patching `ActiveRecord::Base`.

Say I want to add some extra functionality to Active Record. This is what I
would do in Rails 4.2.

```ruby
module MyAwesomeFeature
  def do_something_great
    puts "Doing something complex stuff!!"
  end
end

ActiveRecord::Base.include(MyAwesomeFeature)
```

But now, `ActiveRecord::Base` forever includes `MyAwesomeFeature` and any class
inheriting from it also includes `MyAwesomeFeature` even if they don't want it.

This is especially true if you are using plugins and engines where monkey
patching to `ActiveRecord::Base` can leak into engine or plugin code.

But with `ApplicationRecord`, they will be localized to only those models which
are inheriting from `ApplicationRecord`, effectively only to your application.

```ruby
class ApplicationRecord < ActiveRecord::Base
  include MyAwesomeFeature

  self.abstract_class = true
end
```

## Migrating from Rails 4

By default all new Rails 5 applications will have `application_record.rb`. If
you are migrating from Rails 4, then simply create
`app/models/application_record.rb` as shown below and change all models to
inherit from `ApplicationRecord` instead of `ActiveRecord::Base`.

```ruby
# app/models/application_record.rb
class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true
end
```

## Links

- [Human page](https://www.bigbinary.com/blog/application-record-in-rails-5)