How to cache a custom snippet in Rails 4?

Question

My application (Rails 4) allows users to vote on posts. Is it possible to cache a message, but personalize the voting cache so that it displays one personalized for current_user? For example, whether the user voted or not.

I would prefer not to modify the html structure to achieve this.

# posts/_post.html.slim - cache post do h1 = post.title = post.text = render 'votes/form', post: post # votes/_form.html.slim - if signed_in? && current_user.voted?(post) = form_for current_user.votes.find_by(post: post), method: :delete do |f| = f.submit - else = form_for Vote.new do |f| = f.submit 

Answer 1

You have two options:

Option 1: do not cache voices

This is the simplest solution that I personally recommend. You just don’t cache the dynamic user-dependent part, so you have something like this:

 # posts/_post.html.slim - cache post do h1 = post.title = post.text = render 'votes/form', post: post # not cached 

Option 2: use javascript

This solution is more complex, but it actually does basecamp (however, mostly with simpler examples). You have both parts made on the page, but delete one of them using javascript. Here is an example using jQuery and CoffeeScript:

 # posts/_post.html.slim - cache post do h1 = post.title = post.text = render 'votes/form', post: post # votes/_form.html.slim div#votes{"data-id" => post.id} .not_voted = form_for current_user.votes.find_by(post: post), method: :delete do |f| = f.submit .voted = form_for Vote.new do |f| = f.submit # css .not_voted { display:none; } # javascript (coffeescript) jQuery -> if $('#votes').length $.getScript('/posts/current/' + $('#votes').data('id')) # posts_controller.b def current @post = Post.find(params[:id]) end # users/current.js.erb <% signed_in? && current_user.voted?(@post) %> $('.voted').hide(); $('.not_voted').show(); <% end %> 

Would I, however, change the voted? method correctly voted? to accept the identifier, so you do not need to make a new request. You can learn more about this approach at these railscasts: http://railscasts.com/episodes/169-dynamic-page-caching-revised?view=asciicast

Answer 2

Try the following: it will create 2 different fragments for voting and will not vote for each post. It will be read according to its status.

 # posts/_post.html.slim - cache [post, current_user.votes.find_by(post: post)]do h1 = post.title = post.text = render 'votes/form', post: post