require 'active_support/core_ext/object/duplicable' class Object # Returns a deep copy of object if it's duplicable. If it's # not duplicable, returns +self+. # # object = Object.new # dup = object.deep_dup # dup.instance_variable_set(:@a, 1) # # object.instance_variable_defined?(:@a) # => false # dup.instance_variable_defined?(:@a) # => true def deep_dup duplicable? ? dup : self end end class Array # Returns a deep copy of array. # # array = [1, [2, 3]] # dup = array.deep_dup # dup[1][2] = 4 # # array[1][2] # => nil # dup[1][2] # => 4 def deep_dup map { |it| it.deep_dup } end end class Hash # Returns a deep copy of hash. # # hash = { a: { b: 'b' } } # dup = hash.deep_dup # dup[:a][:c] = 'c' # # hash[:a][:c] # => nil # dup[:a][:c] # => "c" def deep_dup each_with_object(dup) do |(key, value), hash| hash[key.deep_dup] = value.deep_dup end end end