Memoize Method lets you memoize the return value of methods methods with a single word.

cache def my_expensive_computation
  ...
end

Add this line to your application's Gemfile:

gem 'memoize_method'

And then execute:

$ bundle

Or install it yourself as:

$ gem install memoize_method

You are going to want to extend MemoizeMethod in your class

class A
  extend MemoizeMethod
end

irb> A.methods - Object.methods
=> [:cache]

Now lets cache our method.

class A
  extend MemoizeMethod
  cache def foo
    Time.now
  end
end

irb> A.new.methods - Object.new.methods
=> [:foo, :cacheless_foo, :recompute_foo]

Now you have 3 methods where you defined foo,

• foo is will compute the first time, then cache after that.
• cacheless_foo lets you get at the current value without busting the cache.
• recompute_foo will bust the cache and assign it to the new value.

Example:

irb> a = A.new
=> #<A:0x007f98212599f8>
irb> a.foo
=> 2015-11-15 10:38:09 -0800
irb> a.foo
=> 2015-11-15 10:38:09 -0800
irb> a.foo == a.foo
=> true
irb> a.cacheless_foo
=> 2015-11-15 10:38:41 -0800
irb> a.cacheless_foo != a.foo
=> true
irb(main):018:0> a.recompute_foo
=> 2015-11-15 10:41:01 -0800
irb(main):019:0> a.foo
=> 2015-11-15 10:41:01 -0800
irb(main):020:0> a.recompute_foo == a.foo
=> true

After checking out the repo, run bin/setup to install dependencies. Then, run rake false to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/hparker/memoize_method.