Ruby Memoizable decorator experiment (from power-of-trust.net)

Decorators.rb

require 'concurrent'
require 'method_decorators'

# usage in class:
#    include Decorators
module Decorators
	# when module included (hook)
	def self.included(base)
		# some class-methods needed for decorators to work
		base.extend MethodDecorators
	end
	
	# *doesn't work for methods with block_given (will raise exception)
	# *works for methods and class-methods
	# usage in def:
	#    +Memoizable
	#    def method
	# usage in calls:
	#    Test.action(2){:real} | Test.action(2){:flush} — flush cache only for this arg
	#    Test.action{:flush} — flush all cache
	#    Test.action(n:1, b:2) — works correctly for arguments like hash and array
	#    Test.action — works also if no params
	# pass block to memoizable method 'members_uids'
	#		def members_count(&block)
	#			members_uids(count:true, &block)
	#		end
	# so we can now call: g.members_count{:real}
	class Memoizable < MethodDecorators::Decorator
		@@known_flags = {real:1, flush:1}
		attr :cache_map_by_obj_args
		
		# on destroy of some object — remove its using as a key in cache_map_by_obj_args from all existing Memoizable decorators
		# in 'def destroy'
		#		Memoizable.unref self
		def Memoizable.unref(destroyed_o)
			ObjectSpace.each_object(Memoizable) do |decorator|
				decorator.cache_map_by_obj_args.delete destroyed_o
			end
		end
		
		# helps to check if some garbage left after :flush
		# Decorators::Memoizable.stats
		def Memoizable.stats
			ObjectSpace.each_object(Memoizable) {|o| p o }
		end
		# Decorators::Memoizable.total
		def Memoizable.total
			ObjectSpace.each_object(Memoizable).count
		end
		
		
		def initialize
			@cache_map_by_obj_args = {}
		end
		
		#! with calling .destroy there can be problem if some other links to this item still are in use…
		def call(wrapped, this, *args, &blk)
			# (<!) detect flag from block
			if block_given?
				flag = blk.()
				raise NotImplementedError, 'Decorators::Memoizable doesn\'t work for methods with block_given' if !@@known_flags[flag]
			end

			# thread safe Concurrent::Map used here instead of Hash to overcome an error:
			#   `[]=': can't add a new key into hash during iteration (RuntimeError)
			# *Concurrent::Map has better performance than Concurrent::Hash
			#cache_map = @cache_map_by_obj_args[this] ||= {}
			cache_map = @cache_map_by_obj_args[this] ||= Concurrent::Map.new
			
			# (<!) on :flush flag — clear all cache
			if flag == :flush && args.empty?
				for item in cache_map.values
					item.destroy if item.respond_to? :destroy
				end
				# *deletion not needed here, deletion works in Memoizable.unref
				# @cache_map_by_obj_args.delete this
				cache_map.clear
				return
			end
			
			signature = args
			
			# if cached
			if cache_map.key?(signature)
				item = cache_map[signature]
				
				# on :real|:flush flag — clear this cache
				if flag
					item.destroy if item.respond_to? :destroy
					cache_map.delete signature
				else
					# (<!) return cached
					return item
				end
			end

			# cache and return
			cache_map[signature] = wrapped.(*args)
		end
	end
end


class Test
	include Decorators
	
	+Memoizable
	def Test.get_group(n)
		puts "------ get_group #{n} working..."
		{rg:n}
	end
	
	+Memoizable
	def Test.get_group2(n:nil, **others)
		puts "------ get_group2 #{n} working..."
		{rg:n}
	end
	
end

#puts Test.new.method_added   #  — should raise undefined method
# puts Test.method_added   #  — should raise wrong number of arguments
puts Test.get_group 1
puts Test.get_group 1
puts Test.get_group(1){:real}
puts Test.get_group 1
puts Test.get_group2(n:1)
puts Test.get_group2(n:1)
puts Test.get_group2{:flush}
puts Test.get_group2(n:1)


class Group
	include Decorators
	
	+Memoizable
	def members_uids(p:'1', count:false)
		puts 'working'
		"p:"+p
	end

	def members_count(&block)
		members_uids(count:true, &block)
	end
end
g = Group.new
puts g.members_count
puts g.members_count
puts g.members_count{:real}
puts g.members_count

• Презентація Декоратори методів in Ruby
• Більше про проект платформи Сила Довіри — https://power-of-trust.net