memoize
memoize(*symbols)No documentation available.
# File activesupport/lib/active_support/memoizable.rb, line 66
def memoize(*symbols)
symbols.each do |symbol|
original_method = :"_unmemoized_#{symbol}"
memoized_ivar = ActiveSupport::Memoizable.memoized_ivar_for(symbol)
class_eval include InstanceMethods # include InstanceMethods # if method_defined?(:#{original_method}) # if method_defined?(:_unmemoized_mime_type) raise "Already memoized #{symbol}" # raise "Already memoized mime_type" end # end alias #{original_method} #{symbol} # alias _unmemoized_mime_type mime_type # if instance_method(:#{symbol}).arity == 0 # if instance_method(:mime_type).arity == 0 def #{symbol}(reload = false) # def mime_type(reload = false) if reload || !defined?(#{memoized_ivar}) || #{memoized_ivar}.empty? # if reload || !defined?(@_memoized_mime_type) || @_memoized_mime_type.empty? #{memoized_ivar} = [#{original_method}] # @_memoized_mime_type = [_unmemoized_mime_type] end # end #{memoized_ivar}[0] # @_memoized_mime_type[0] end # end else # else def #{symbol}(*args) # def mime_type(*args) #{memoized_ivar} ||= {} unless frozen? # @_memoized_mime_type ||= {} unless frozen? args_length = method(:#{original_method}).arity # args_length = method(:_unmemoized_mime_type).arity if args.length == args_length + 1 && # if args.length == args_length + 1 && (args.last == true || args.last == :reload) # (args.last == true || args.last == :reload) reload = args.pop # reload = args.pop end # end # if defined?(#{memoized_ivar}) && #{memoized_ivar} # if defined?(@_memoized_mime_type) && @_memoized_mime_type if !reload && #{memoized_ivar}.has_key?(args) # if !reload && @_memoized_mime_type.has_key?(args) #{memoized_ivar}[args] # @_memoized_mime_type[args] elsif #{memoized_ivar} # elsif @_memoized_mime_type #{memoized_ivar}[args] = #{original_method}(*args) # @_memoized_mime_type[args] = _unmemoized_mime_type(*args) end # end else # else #{original_method}(*args) # _unmemoized_mime_type(*args) end # end end # end end # end # if private_method_defined?(#{original_method.inspect}) # if private_method_defined?(:_unmemoized_mime_type) private #{symbol.inspect} # private :mime_type elsif protected_method_defined?(#{original_method.inspect}) # elsif protected_method_defined?(:_unmemoized_mime_type) protected #{symbol.inspect} # protected :mime_type end # end, __FILE__, __LINE__ + 1
end
end4Notes
Need to extend class when using this
I had to dig around to find this out - if you want to use memoize somewhere, like an ActiveRecord model, you need to add
extend ActiveSupport::Memoizable
to the class. This doesn't seem to be explained anywhere (the only docs are 3 year old blog posts anyway).
Example from Code School
module Tweets
class ShowPresenter
extend ActiveSupport::Memoizable
def initialize(tweet)
@tweet = tweet
end
def username
@tweet.user.username
end
def status
@tweet.status
end
def favorites_count
@tweet.favorites.count
end
memoize :username, :status, :favorites_count
end
end
this has been deprecated; replace with Memoist
In Rails 3.2, memoize has been deprecated. In edge Rails, it has been removed.
The commit when it was deprecated: http://github.com/rails/rails/commit/36253916b0b788d6ded56669d37c96ed05c92c5c
A Stack Overflow question about this change: http://stackoverflow.com/q/9132197/578288
I personally disagree with the removal of memoize, and don’t recommend using the ||= pattern Rails now suggests. The exception is if your entire program only memoizes something once or twice, so it’s not worth including a gem for.
The easiest way to keep using memoize is to use the Memoist gem (http://github.com/matthewrudy/memoist , http://rubygems.org/gems/memoist), which is a simple extraction of ActiveSupport::Memoizable into its own gem.
instead of memoize
See this for deprecated https://github.com/rails/rails/commit/36253916b0b788d6ded56669d37c96ed05c92c5c
use
def something
return @_var if defined? @_var
# more code
end