Even though this has worked it’s annoying to have to remember to make this change every time we change a template and this is where the Cache Digests gem comes in useful. This functionality will be available by default in Rails 4 but has been extracted out into a gem so that we can use it in Rails 3 projects. This gem works by including a digest in the fragment cache keys that is based on the templates. This means that if the template changes a new cache key is generated and that cache will expire. We’ll try this gem in our application. As ever we use it by adding it to our gemfile then running bundle to install it.