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.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)

You can set the default value from the database declaration, like:

create_table :conversations do |t|
  t.column :status, :integer, default: 0
end

Good practice is to let the first declared status be the default.

Finally, it's also 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

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 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

Methods

enum

Constants

ENUM_CONFLICT_MESSAGE

\ "You tried to define an enum named \"%{enum}\" on the model \"%{klass}\", but " \ "this will generate a %{type} method \"%{method}\", which is already defined " \ "by %{source}."

Instance Public methods

enum(definitions)

📝 Source code

# File activerecord/lib/active_record/enum.rb, line 151
    def enum(definitions)
      klass = self
      enum_prefix = definitions.delete(:_prefix)
      enum_suffix = definitions.delete(:_suffix)
      definitions.each do |name, values|
        # statuses = { }
        enum_values = ActiveSupport::HashWithIndifferentAccess.new
        name = name.to_s

        # def self.statuses() statuses end
        detect_enum_conflict!(name, name.pluralize, true)
        singleton_class.send(:define_method, name.pluralize) { enum_values }
        defined_enums[name] = enum_values

        detect_enum_conflict!(name, name)
        detect_enum_conflict!(name, "#{name}=")

        attr = attribute_alias?(name) ? attribute_alias(name) : name
        decorate_attribute_type(attr, :enum) do |subtype|
          EnumType.new(attr, enum_values, subtype)
        end

        _enum_methods_module.module_eval do
          pairs = values.respond_to?(:each_pair) ? values.each_pair : values.each_with_index
          pairs.each do |label, value|
            if enum_prefix == true
              prefix = "#{name}_"
            elsif enum_prefix
              prefix = "#{enum_prefix}_"
            end
            if enum_suffix == true
              suffix = "_#{name}"
            elsif enum_suffix
              suffix = "_#{enum_suffix}"
            end

            value_method_name = "#{prefix}#{label}#{suffix}"
            enum_values[label] = value
            label = label.to_s

            # def active?() status == "active" end
            klass.send(:detect_enum_conflict!, name, "#{value_method_name}?")
            define_method("#{value_method_name}?") { self[attr] == label }

            # def active!() update!(status: 0) end
            klass.send(:detect_enum_conflict!, name, "#{value_method_name}!")
            define_method("#{value_method_name}!") { update!(attr => value) }

            # scope :active, -> { where(status: 0) }
            klass.send(:detect_enum_conflict!, name, value_method_name, true)
            klass.scope value_method_name, -> { where(attr => value) }
          end
        end
        enum_values.freeze
      end
    end

🔎 See on GitHub