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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"

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
E

Instance Public methods

enum(definitions)

Source: show | on GitHub 

# File activerecord/lib/active_record/enum.rb, line 158
def enum(definitions)
  enum_prefix = definitions.delete(:_prefix)
  enum_suffix = definitions.delete(:_suffix)
  enum_scopes = definitions.delete(:_scopes)

  default = {}
  default[:default] = definitions.delete(:_default) if definitions.key?(:_default)

  definitions.each do |name, values|
    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}=")

    attr = attribute_alias?(name) ? attribute_alias(name) : name

    decorate_attribute_type(attr, **default) do |subtype|
      EnumType.new(attr, enum_values, subtype)
    end

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

      suffix = if enum_suffix == true
        "_#{name}"
      elsif enum_suffix
        "_#{enum_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, enum_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, enum_scopes)
        end
      end
    end
    detect_negative_enum_conditions!(value_method_names) if enum_scopes != false
    enum_values.freeze
  end
end