Which Ruby memoize pattern does ActiveSupport::Memoizable refer to?

Question

So in Rails 3.2, ActiveSupport::Memoizable has been deprecated.

The message reads:

DEPRECATION WARNING: ActiveSupport::Memoizable is deprecated and
will          


        

Answer 1

Another option is to use the Memoist gem:

• Memoist on GitHub
• Memoist on RubyGems

It is a direct extraction from ActiveSupport::Memoizable and can be used as a drop-in replacement. Just require 'memoist' and change

extend ActiveSupport::Memoizable

to

extend Memoist

Answer 2

Based upon the comments on the commit referenced above by avaynshtok, I’m going with this:

ActiveSupport::Deprecation.silence { extend ActiveSupport::Memoizable }

… because I figure I’ll know when Memoizable is ripped out of ActiveSupport from my RSpec suite dying right out of the starting gate.

Answer 3

Just an addition to the top answer, to memoize a class method use the following pattern:

class Foo
  class << self
    def bar
      @bar ||= begin
        # ...
      end
    end
  end
end

Answer 4

Here is the commit (and subsequent discussion) where Memoizable was deprecated: https://github.com/rails/rails/commit/36253916b0b788d6ded56669d37c96ed05c92c5c

The author advocates the @foo ||= ... approach and points to this commit as an example for migration: https://github.com/rails/rails/commit/f2c0fb32c0dce7f8da0ce446e2d2f0cba5fd44b3.

Edit: Note that I don't necessarily interpret this change as meaning that all instances of memoize can or should be replaced w/ this pattern. I read it as meaning that Memoizable is no longer needed/wanted in the Rails code itself. As the comments point out, Memoizable is much more than just a wrapper around @foo ||= .... If you need those features, go ahead and use Memoizable, you'll just have to get it from somewhere other than ActiveSupport (I'm guessing someone will fork a gem version, if they haven't already).