Better selects for ActiveRecord

select.rb

class << ActiveRecord::Base
  prepend Module.new {
    class SelectChain < BasicObject
      INVALID_ARGUMENTS =
        '.select.not arguments must be a list of one or more symbols'.freeze

      def initialize(scope)
        @scope = scope
      end

      def method_missing(method_name, *arguments, &block)
        select.public_send(method_name, *arguments, &block)
      end

      def not(*columns)
        if columns.empty? || (columns - scope_columns).any?
          raise ArgumentError, ERROR
        end
        select(scope_columns - columns)
      end

      private

      def select(columns = scope_columns)
        @select ||= @scope.select(*columns)
      end

      def scope_columns
        @scope.column_names.map(&:to_sym)
      end
    end

    def select(chain = :chain, *)
      !block_given? && chain == :chain ? SelectChain.new(all.spawn) : super
    end
  }
end