encoded attribute example

encoded_attr.rb

module EncodedAttr
  ENCODINGS = %i(raw b64 url_b64)

  module ClassMethods
    def encoded_attr(name, default_encoding:, encodings: ENCODINGS)
      raise ArgumentError unless ENCODINGS.include?(default_encoding)

      encodings.each do |encoding|
        if encoding == default_encoding
          alias_method "#{encoding}_#{name}", name
          alias_method "#{encoding}_#{name}=", "#{name}="
        else
          define_method("#{encoding}_#{name}") do
            encode_val(decode_val(send(name), default_encoding), encoding)
          end

          define_method("#{encoding}_#{name}=") do |new_val|
            send("#{name}=", encode_val(decode_val(new_val, encoding), default_encoding))
          end
        end
      end
    end
  end

  def self.included(base_class)
    base_class.extend(ClassMethods)
  end

  def encode_val(value, encoding)
    case encoding
    when :raw
      value
    when :b64
      Base64.strict_encode64(value)
    when :url_b64
      Base64.urlsafe_encode64(value)
    end
  end

  def decode_val(value, encoding)
    case encoding
    when :raw
      value
    when :b64
      Base64.strict_decode64(value)
    when :url_b64
      Base64.urlsafe_decode64(value)
    end
  end
end

test.rb

require "base64"

class TestClass
  include EncodedAttr

  attr_accessor :one, :two, :three

  encoded_attr :one,   default_encoding: :raw
  encoded_attr :two,   default_encoding: :b64
  encoded_attr :three, default_encoding: :url_b64
end

def assert_equal(a, b)
  raise "expected '#{a}'=='#{b}'" unless a == b
end

x = TestClass.new

x.raw_one = "one"
assert_equal x.one, "one"
assert_equal x.raw_one, "one"
assert_equal x.b64_one, "b25l"
assert_equal x.url_b64_one, "b25l"

x.b64_one = "b25l"
assert_equal x.one, "one"
assert_equal x.raw_one, "one"
assert_equal x.b64_one, "b25l"
assert_equal x.url_b64_one, "b25l"

x.url_b64_one = "b25l"
assert_equal x.one, "one"
assert_equal x.raw_one, "one"
assert_equal x.b64_one, "b25l"
assert_equal x.url_b64_one, "b25l"

x.raw_two = "two"
assert_equal x.two, "dHdv"
assert_equal x.raw_two, "two"
assert_equal x.b64_two, "dHdv"
assert_equal x.url_b64_two, "dHdv"

x.b64_two = "dHdv"
assert_equal x.two, "dHdv"
assert_equal x.raw_two, "two"
assert_equal x.b64_two, "dHdv"
assert_equal x.url_b64_two, "dHdv"

x.url_b64_two = "dHdv"
assert_equal x.two, "dHdv"
assert_equal x.raw_two, "two"
assert_equal x.b64_two, "dHdv"
assert_equal x.url_b64_two, "dHdv"

x.raw_three = "three"
assert_equal x.three, "dGhyZWU="
assert_equal x.raw_three, "three"
assert_equal x.b64_three, "dGhyZWU="
assert_equal x.url_b64_three, "dGhyZWU="

x.b64_three = "dGhyZWU="
assert_equal x.three, "dGhyZWU="
assert_equal x.raw_three, "three"
assert_equal x.b64_three, "dGhyZWU="
assert_equal x.url_b64_three, "dGhyZWU="

x.url_b64_three = "dGhyZWU="
assert_equal x.three, "dGhyZWU="
assert_equal x.raw_three, "three"
assert_equal x.b64_three, "dGhyZWU="
assert_equal x.url_b64_three, "dGhyZWU="

puts "ok"

test.sh

#!/bin/bash

ruby -I. -rencoded_attr test.rb