module ActiveRecord::Enum

Declare an enum attribute where the values map to integers in the database, but can be queried by name. Example:

class Conversation < ActiveRecord::Base
  enum :status, [ :active, :archived ]
end

# conversation.update! status: 0
conversation.active!
conversation.active? # => true
conversation.status  # => "active"

# conversation.update! status: 1
conversation.archived!
conversation.archived? # => true
conversation.status    # => "archived"

# conversation.status = 1
conversation.status = "archived"

conversation.status = nil
conversation.status.nil? # => true
conversation.status      # => nil

Scopes based on the allowed values of the enum field will be provided as well. With the above example:

Conversation.active
Conversation.not_active
Conversation.archived
Conversation.not_archived

Of course, you can also query them directly if the scopes don’t fit your needs:

Conversation.where(status: [:active, :archived])
Conversation.where.not(status: :active)

Defining scopes can be disabled by setting :scopes to false.

class Conversation < ActiveRecord::Base
  enum :status, [ :active, :archived ], scopes: false
end

You can set the default enum value by setting :default, like:

class Conversation < ActiveRecord::Base
  enum :status, [ :active, :archived ], default: :active
end

conversation = Conversation.new
conversation.status # => "active"

It’s possible to explicitly map the relation between attribute and database integer with a hash:

class Conversation < ActiveRecord::Base
  enum :status, active: 0, archived: 1
end

Finally it’s also possible to use a string column to persist the enumerated value. Note that this will likely lead to slower database queries:

class Conversation < ActiveRecord::Base
  enum :status, active: "active", archived: "archived"
end

Note that when an array is used, the implicit mapping from the values to database integers is derived from the order the values appear in the array. In the example, :active is mapped to 0 as it’s the first element, and :archived is mapped to 1. In general, the i-th element is mapped to i-1 in the database.

Therefore, once a value is added to the enum array, its position in the array must be maintained, and new values should only be added to the end of the array. To remove unused values, the explicit hash syntax should be used.

In rare circumstances you might need to access the mapping directly. The mappings are exposed through a class method with the pluralized attribute name, which return the mapping in a ActiveSupport::HashWithIndifferentAccess :

Conversation.statuses[:active]    # => 0
Conversation.statuses["archived"] # => 1

Use that class method when you need to know the ordinal value of an enum. For example, you can use that when manually building SQL strings:

Conversation.where("status <> ?", Conversation.statuses[:archived])

You can use the :prefix or :suffix options when you need to define multiple enums with same values. If the passed value is true, the methods are prefixed/suffixed with the name of the enum. It is also possible to supply a custom value:

class Conversation < ActiveRecord::Base
  enum :status, [ :active, :archived ], suffix: true
  enum :comments_status, [ :active, :inactive ], prefix: :comments
end

With the above example, the bang and predicate methods along with the associated scopes are now prefixed and/or suffixed accordingly:

conversation.active_status!
conversation.archived_status? # => false

conversation.comments_inactive!
conversation.comments_active? # => false

If you want to disable the auto-generated methods on the model, you can do so by setting the :instance_methods option to false:

class Conversation < ActiveRecord::Base
  enum :status, [ :active, :archived ], instance_methods: false
end

If you want the enum value to be validated before saving, use the option :validate:

class Conversation < ActiveRecord::Base
  enum :status, [ :active, :archived ], validate: true
end

conversation = Conversation.new

conversation.status = :unknown
conversation.valid? # => false

conversation.status = nil
conversation.valid? # => false

conversation.status = :active
conversation.valid? # => true

It is also possible to pass additional validation options:

class Conversation < ActiveRecord::Base
  enum :status, [ :active, :archived ], validate: { allow_nil: true }
end

conversation = Conversation.new

conversation.status = :unknown
conversation.valid? # => false

conversation.status = nil
conversation.valid? # => true

conversation.status = :active
conversation.valid? # => true

Otherwise ArgumentError will raise:

class Conversation < ActiveRecord::Base
  enum :status, [ :active, :archived ]
end

conversation = Conversation.new

conversation.status = :unknown # 'unknown' is not a valid status (ArgumentError)