Rails 7 Introduces a New Syntax for Enum

Rails 7 introduces a new syntax for defining enum. Lets take a look what has changed.

What is enum in Rails?

Enum ( Enumeration ) is a datatype available in Rails, which can be used to map values to integral values in the database, which means it takes less space and provides the efficiency requires. It allows the flexiblity to query it by name, makes it even better candidate to use where you want to define multiple values of same attribute. For example, post status can be draft or published.

Old vs. New: A Quick Look

In the old days, defining enum involved a key-value pair, but not anymore! Rails 7 separates enum names and values, making your code more straightforward:

# Before
enum status: [ :draft, :published, :archived ], _prefix: true, _scopes: false

# After
enum :status, [ :draft, :published, :archived ], prefix: true, scopes: false

Defining enum with hash syntax

The changes in rails are seamlessly extends the use of hash syntax as well, lets take a look in folowing example.

# Hash syntax
enum :status, { draft: 0, published: 1, archived: 2 }, prefix: true, scopes: false

Why did they changed the enum syntax in Rails 7?

Based on the discussion on this PR#41328, that is due to enum takes on hash argument only, which contains both enum definitions and reserved options. To avoid leading an underscore from reserved options as in _prefix for example. This new syntax was introduced.

Is the old enum syntax deprecated?

The old way of defining an enum is not yet deprecated. Following way of defining is still valid as of Rails 7.1.3.

class Post < ApplicationRecord
  enum status: [:draft, :published]
end

** Please note that the new `enum` validation options as mentioned in the Article will result in error if you try to use it with old syntax.

class Post < ApplicationRecord
  enum status: [:draft, :published], validate: true
end

post = Post.new
#
# => `raise_conflict_error`: You tried to define an enum named "status" on the model "Post", but this will generate a instance method "draft?", which is already defined by another enum. (ArgumentError)