Rails%203%20In%20Action

460 CHAPTER 16 Basic performance enhancements
You’ve now seen many different flavors of controller caching, ranging from caching
pages and caching actions (actually, fragments), to getting the browser to take care of
the hard part of the caching process (storing a file and expiring it). All of these caching
methods deal with caching entire pages, so what’s a Railer supposed to do if they
want to cache only a bit of a page at a time? For that, you can tell Rails to cache just
these parts using an aptly named method: cache.
16.3.5 Caching page fragments
If part of a page takes a long time to render, then that’s a problem. To fix this kind of
problem, you can use fragment caching, which allows you to cache fragments of pages
using the cache method in your views where appropriate. This method takes a block,
like this:
# some horribly long and complex thing
This way, when Rails attempts to load the page and comes across your cache call, it will
check to see if there’s an available fragment for it. Otherwise it will perform the code
inside the block and then store it in tmp/cache, just like caches_action does for an
entire page.
You don’t have an actual use-case for this in your application at the moment, but
you’ll still use it just to see what it does. You’re going to be using it back on the app/
views/projects/show.html.erb view, meaning you’re going to want to temporarily disable
caches_action in ProjectsController for this action so that it doesn’t cache
the page before cache has a chance to run. You can do this by simply removing the
lines in ProjectsController:
# caches_action :show, :cache_path => (proc do
# project_path(params[:id]) + "/#{current_user.id}/#{params[:page] || 1}"
# end)
In the app/views/projects/show.html.erb, the primary content that’s going to be
changing is the list of tickets, and so you’ll want to cache that and leave out the rest.
To do this, you’ll wrap the whole list of tickets, including the pagination link above it,
in a cache block, as shown in the following listing.
Listing 16.5 app/views/projects/show.html.erb
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