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

Constants

ENUM_CONFLICT_MESSAGE

Public Instance Methods

enum(name = nil, values = nil, **options) click to toggle source
# File lib/active_record/enum.rb, line 167
def enum(name = nil, values = nil, **options)
  if name
    values, options = options, {} unless values
    return _enum(name, values, **options)
  end

  definitions = options.slice!(:_prefix, :_suffix, :_scopes, :_default)
  options.transform_keys! { |key| :"#{key[1..-1]}" }

  definitions.each { |name, values| _enum(name, values, **options) }
end

Private Instance Methods

_enum(name, values, prefix: nil, suffix: nil, scopes: true, **options) click to toggle source
# File lib/active_record/enum.rb, line 180
def _enum(name, values, prefix: nil, suffix: nil, scopes: true, **options)
  assert_valid_enum_definition_values(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.define_method(name.pluralize) { enum_values }
  defined_enums[name] = enum_values

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

  attribute(name, **options) do |subtype|
    subtype = subtype.subtype if EnumType === subtype
    EnumType.new(name, enum_values, subtype)
  end

  value_method_names = []
  _enum_methods_module.module_eval do
    prefix = if prefix
      prefix == true ? "#{name}_" : "#{prefix}_"
    end

    suffix = if suffix
      suffix == true ? "_#{name}" : "_#{suffix}"
    end

    pairs = values.respond_to?(:each_pair) ? values.each_pair : values.each_with_index
    pairs.each do |label, value|
      enum_values[label] = value
      label = label.to_s

      value_method_name = "#{prefix}#{label}#{suffix}"
      value_method_names << value_method_name
      define_enum_methods(name, value_method_name, value, scopes)

      method_friendly_label = label.gsub(/[\W&&[:ascii:]]+/, "_")
      value_method_alias = "#{prefix}#{method_friendly_label}#{suffix}"

      if value_method_alias != value_method_name && !value_method_names.include?(value_method_alias)
        value_method_names << value_method_alias
        define_enum_methods(name, value_method_alias, value, scopes)
      end
    end
  end
  detect_negative_enum_conditions!(value_method_names) if scopes
  enum_values.freeze
end
_enum_methods_module() click to toggle source
# File lib/active_record/enum.rb, line 261
def _enum_methods_module
  @_enum_methods_module ||= begin
    mod = EnumMethods.new(self)
    include mod
    mod
  end
end
assert_valid_enum_definition_values(values) click to toggle source
# File lib/active_record/enum.rb, line 269
      def assert_valid_enum_definition_values(values)
        unless values.is_a?(Hash) || values.all?(Symbol) || values.all?(String)
          error_message = <<~MSG
            Enum values #{values} must be either a hash, an array of symbols, or an array of strings.
          MSG
          raise ArgumentError, error_message
        end

        if values.is_a?(Hash) && values.keys.any?(&:blank?) || values.is_a?(Array) && values.any?(&:blank?)
          raise ArgumentError, "Enum label name must not be blank."
        end
      end
detect_enum_conflict!(enum_name, method_name, klass_method = false) click to toggle source
# File lib/active_record/enum.rb, line 288
def detect_enum_conflict!(enum_name, method_name, klass_method = false)
  if klass_method && dangerous_class_method?(method_name)
    raise_conflict_error(enum_name, method_name, type: "class")
  elsif klass_method && method_defined_within?(method_name, Relation)
    raise_conflict_error(enum_name, method_name, type: "class", source: Relation.name)
  elsif !klass_method && dangerous_attribute_method?(method_name)
    raise_conflict_error(enum_name, method_name)
  elsif !klass_method && method_defined_within?(method_name, _enum_methods_module, Module)
    raise_conflict_error(enum_name, method_name, source: "another enum")
  end
end
detect_negative_enum_conditions!(method_names) click to toggle source
# File lib/active_record/enum.rb, line 310
def detect_negative_enum_conditions!(method_names)
  return unless logger

  method_names.select { |m| m.start_with?("not_") }.each do |potential_not|
    inverted_form = potential_not.sub("not_", "")
    if method_names.include?(inverted_form)
      logger.warn "Enum element '#{potential_not}' in #{self.name} uses the prefix 'not_'." \
        " This has caused a conflict with auto generated negative scopes." \
        " Avoid using enum elements starting with 'not' where the positive form is also an element."
    end
  end
end
raise_conflict_error(enum_name, method_name, type: "instance", source: "Active Record") click to toggle source
# File lib/active_record/enum.rb, line 300
def raise_conflict_error(enum_name, method_name, type: "instance", source: "Active Record")
  raise ArgumentError, ENUM_CONFLICT_MESSAGE % {
    enum: enum_name,
    klass: name,
    type: type,
    method: method_name,
    source: source
  }
end