Read out enum values from Postgres with ActiveRecord

pg_enum.rb

class PgEnum
  attr_reader :type

  def initialize(type)
    @type = type.to_s
  end

  class << self
    alias_method :for_type, :new
  end

  def values
    @values ||= begin
      q = "select unnest(enum_range(null::#{@type})) as value"
      ActiveRecord::Base.connection.execute(q).values.flatten
    end
  rescue ActiveRecord::StatementInvalid => ex
    Rails.logger.warn("#{@type} does not exists\n#{ex.backtrace}")
    []
  end
end

pg_enum_spec.rb

require 'rails_helper'

describe PgEnum do
  describe '#values' do
    context 'with existing type' do
      around(:example) do |ex|
        ActiveRecord::Base.connection.execute("CREATE TYPE my_enum as ENUM ('apple', 'orange')")
        ex.run
        ActiveRecord::Base.connection.execute('DROP TYPE my_enum')
      end
      let(:enum) { PgEnum.for_type(:my_enum) }

      it 'returns all values as an array' do
        expect(enum.values).to eq(%w[apple orange])
      end
    end

    it 'returns an empty array for non-existent types' do
      enum = PgEnum.for_type(:non_existent)

      expect(Rails.logger).to receive(:warn)
      expect(enum.values).to eq([])
    end
  end
end