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comp.lang.ruby

[ANN] Cache Decorator

Jake McArthur

7/21/2006 2:06:00 PM

This isn't really anything that hasn't been done before, but I have
yet to see some public Ruby code that provides a nice, easy way to
cache the results of methods with this much flexibility and
convenience. Simply wrap an object in a CacheDecorator object, and
cache away. Method results are stored for each set of arguments that
are passed to it. You can choose which methods of the object are
cached, invalidate caches manually, stop caching methods, set whether
the caches expire after some amount of time, and even set some
methods to invalidate the caches of other methods of the same object.
We cache things pretty often when things are too slow, but let's not
use a bunch of those extra variables that make code so much harder to
read. Simple example:

obj = CacheDecorator.new(obj)
obj.cache :foo # caches foo
obj.cache :bar, 5 # caches bar with an expiry time of 5 seconds
loop do
puts obj.foo # stays the same the whole time
puts obj.bar # changes every five seconds
end

This is actually something I worked on a long time ago. I just didn't
ever announce it. Also, it's been a long time since it was updated,
but I intend to add a few more features/conveniences to it pretty soon.

Get it here: http://rubyforge.org/projects/cache-...

- Jake McArthur
2 Answers

Mike Harris

7/21/2006 3:09:00 PM

0

Jake McArthur wrote:

> This isn't really anything that hasn't been done before, but I have
> yet to see some public Ruby code that provides a nice, easy way to
> cache the results of methods with this much flexibility and
> convenience. Simply wrap an object in a CacheDecorator object, and
> cache away. Method results are stored for each set of arguments that
> are passed to it. You can choose which methods of the object are
> cached, invalidate caches manually, stop caching methods, set whether
> the caches expire after some amount of time, and even set some
> methods to invalidate the caches of other methods of the same object.
> We cache things pretty often when things are too slow, but let's not
> use a bunch of those extra variables that make code so much harder to
> read. Simple example:
>
> obj = CacheDecorator.new(obj)
> obj.cache :foo # caches foo
> obj.cache :bar, 5 # caches bar with an expiry time of 5 seconds
> loop do
> puts obj.foo # stays the same the whole time
> puts obj.bar # changes every five seconds
> end
>
> This is actually something I worked on a long time ago. I just didn't
> ever announce it. Also, it's been a long time since it was updated,
> but I intend to add a few more features/conveniences to it pretty soon.
>
> Get it here: http://rubyforge.org/projects/cache-...
>
> - Jake McArthur
>
>
What do you feel are the pros and cons vs. memoize?

Jake McArthur

7/21/2006 4:27:00 PM

0

> What do you feel are the pros and cons vs. memoize?

I haven't really done a benchmark to compare them directly, but
memoization does not allow a cache to expire or invalidate, which
makes it less useful for many cases. On the other hand, memoize
allows you to cache to a file instead of just memory. Memoize is also
still a bit cleaner right now as far as usage goes, but I plan on
modifying and extending Cache Decorator pretty soon.

- Jake McArthur