String enums are useful when you want to keep the actual string instead of integer in database, This gist add the validation to make sure users are passing correct values to model.

string_enums.rb

require 'active_support/concern'

module StringEnums
  extend ActiveSupport::Concern

  class_methods do
    def string_enum(enums_hash)
      enum_name = enums_hash.keys.first.to_s

      define_singleton_method(enum_name.pluralize) do
        result = {}
        enums_hash[enum_name.to_sym].each { |enum_key| result[enum_key] = I18n.t("enums.#{enum_name}.enum_key", :default => enum_key.to_s) }
        result
      end

      validation_method = "validate_#{enum_name}_values"
      validate validation_method.to_sym

      define_method(validation_method) do
        value = send(enum_name)
        errors.add(enum_name, I18n.t("validations.invalid_#{enum_name}", default: "Invalid value for #{enum_name}, possible values are: #{self.class.send(enum_name.pluralize).values}")) unless value.blank? or self.class.send(enum_name.pluralize).keys.include?(value.to_sym)
      end
    end
  end
end

user.rb

# Sample usage of above concern

class User < ActiveRecord::Base
  include StringEnums
  
  string_enum user_group: %i[admin manager developer reporter]
end

Of course in above sample you need to create the user_group column in database as a string with this migration:

class AddUserGroupToUsers < ActiveRecord::Migration
  def change
    add_column :users, :user_group, :string
  end
end