vendor/rails/activesupport/lib/active_support/memoizable.rb

   1 module ActiveSupport
   2   module Memoizable
   3     MEMOIZED_IVAR = Proc.new do |symbol|
   4       "@_memoized_#{symbol.to_s.sub(/\?\Z/, '_query').sub(/!\Z/, '_bang')}".to_sym
   5     end
   6
   7     module Freezable
   8       def self.included(base)
   9         base.class_eval do
  10           unless base.method_defined?(:freeze_without_memoizable)
  11             alias_method_chain :freeze, :memoizable
  12           end
  13         end
  14       end
  15
  16       def freeze_with_memoizable
  17         memoize_all unless frozen?
  18         freeze_without_memoizable
  19       end
  20
  21       def memoize_all
  22         methods.each do |m|
  23           if m.to_s =~ /^_unmemoized_(.*)/
  24             if method(m).arity == 0
  25               __send__($1)
  26             else
  27               ivar = MEMOIZED_IVAR.call($1)
  28               instance_variable_set(ivar, {})
  29             end
  30           end
  31         end
  32       end
  33
  34       def unmemoize_all
  35         methods.each do |m|
  36           if m.to_s =~ /^_unmemoized_(.*)/
  37             ivar = MEMOIZED_IVAR.call($1)
  38             instance_variable_get(ivar).clear if instance_variable_defined?(ivar)
  39           end
  40         end
  41       end
  42     end
  43
  44     def memoize(*symbols)
  45       symbols.each do |symbol|
  46         original_method = :"_unmemoized_#{symbol}"
  47         memoized_ivar = MEMOIZED_IVAR.call(symbol)
  48
  49         class_eval <<-EOS, __FILE__, __LINE__
  50           include Freezable
  51
  52           raise "Already memoized #{symbol}" if method_defined?(:#{original_method})
  53           alias #{original_method} #{symbol}
  54
  55           if instance_method(:#{symbol}).arity == 0
  56             def #{symbol}(reload = false)
  57               if reload || !defined?(#{memoized_ivar}) || #{memoized_ivar}.empty?
  58                 #{memoized_ivar} = [#{original_method}.freeze]
  59               end
  60               #{memoized_ivar}[0]
  61             end
  62           else
  63             def #{symbol}(*args)
  64               #{memoized_ivar} ||= {} unless frozen?
  65               reload = args.pop if args.last == true || args.last == :reload
  66
  67               if defined?(#{memoized_ivar}) && #{memoized_ivar}
  68                 if !reload && #{memoized_ivar}.has_key?(args)
  69                   #{memoized_ivar}[args]
  70                 elsif #{memoized_ivar}
  71                   #{memoized_ivar}[args] = #{original_method}(*args).freeze
  72                 end
  73               else
  74                 #{original_method}(*args)
  75               end
  76             end
  77           end
  78         EOS
  79       end
  80     end
  81   end
  82 end