Alessandro Fazzi alessandro-fazzi

Why I think an "open" decorator is mostly a bad idea

First thing first: when I speak about open decorators I mostly refer to the delegate_all (anti)pattern introduced in many Rails applications by the widely used draper gem. With "open" adjective I refer to the fact that the decorator responds to all the messages as the underlying decorated object. This is like a transparent ill variation of the proxy pattern: if you need proxy pattern[^1] then you want to re-bound the interface, lowering required knowledge as much as you can, lowering responsibilities and lowering the maintenance of boundaries between objects and application layers as much as you are able to.

Draper is a (sort of) presenter

While the family of decoration patterns[^2] is large and with subtle differences between one member and another, I consider Draper's decorators as decorators for the view layer, thus we could speak more of a presenter[^3]. The readme of the gem itself says

	# frozen_string_literal: true

	source 'https://rubygems.org'

	# gem "rails"
	gem 'benchmark-ips'
	gem 'rubocop'
	gem 'stackprof'
	gem 'stackprof-webnav'

	module ValidatableMethods
	def self.included(base)
	base.extend ClassMethods
	end

	module ClassMethods
	def validated(method_name, &block)
	mod = Module.new
	mod.define_method(method_name) do \|args, *kwargs\|
	begin

	ButtonClasses = Struct.new(:classes, :variants, :defaults, keyword_init: true) do \|klass\|
	def render(**settings)
	result = []

	# Add the default classes if any provided
	result << classes if classes

	# Keep the applied variants so we can later apply the defaults
	applied_options = []

	# CLOSURES IN RUBY Paul Cantrell https://innig.net
	# Email: username "paul", domain name "innig.net"

	# I recommend executing this file, then reading it alongside its output.
	#
	# Alteratively, you can give yourself an unreasonable Ruby test by deleting all
	# the comments, then trying to guess the output of the code!
	#
	# (Naive HR departments, please do not use that idea as a hiring quiz.)

	source 'https://rubygems.org'

	gem 'light-service'
	gem 'dry-auto_inject'
	gem 'pry-byebug'