Cory O'Daniel – These are just words Software development, thoughts, and randomness

Expiring rails fragement caches using an expires time instead of a sweeper (expires_in) – (a ‘duh’ post)

So, I'm setting up fragment caching for some stuff, and I honestly don't care about setting up an observer to sweep some stuff. I just want to cache this one slow fragment for like 5 minutes. I've seen these tutorials all over the web that shows people using the expires_in setting to auto-expire cache like so:

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Rails.cache.write('test_key', 'test_value', :expires_in => 5.minutes)

That's great and all, but how the hell do I use it for a Page, Action or Fragment cache? Well you just pass the same :expires_in param and yay it works as long as its a mem_cache_store (although, I did see a hackaroo for file_store)

Even the Rails Guide on caching mentions 'expires_in' but doesn't show how to use it.

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class StupidController < ApplicationController
  caches_page :whatever, :expires_in => 5.minutes
end

What really got me was when I was trying to use it with a fragment cache. I tried this and it didn't work:

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- cache(:action => 'home', :action_suffix => 'advertisements', :expires_in => 10.minutes) do

Why? Well, the cache method takes two hashes, and if you leave off the curly braces, that expires_in ends up in the first one, which is used for the name... To roll it right do:

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- cache({:action => 'home', :action_suffix => 'advertisements'}, :expires_in => 10.minutes) do

Duh, the more you know.