Invalidate a specific model in the Rails cache

Question

I'm using Rails 3 with Memcached to cache some models. When the model changes, I want to invalidate the cache for that record. With view fragments, I just say expire_fragment("blah"). How do I do this with my models? I don't want to say Rails.cache.clear and lose the whole thing. I want something like Rails.cache.invalidate("/users/5"). How do I do that?

Answer 1

You did not mention at what point the model is actually added to the cache. You could try invalidating the model cache using the after_save hook.

class Model < AR::Base

  after_save :invalidate_cache

  private
  def invalidate_cache
     Rails.cache.delete("/users/#{self.id}")
     return true # recommended to return true, as Rails.cache.delete will return false if no cache is found and break the callback chain. 
  end
end