Render rails partial multiple times on same page

Question

I have a partial that I'm rendering twice on the same page, but in two different locations (one is shown during standard layout, one is shown during mobile/tablet layout).

The partial is rendered exactly the same in both places, so I'd like to speed it up by storing it as a variable if possible; the partial makes an API call each time, and the 2nd call is completely unnecessary since it's a duplicate of the first API call.

Is there any way to store the HTML from the returned partial as a variable and then use that for both renders?

Edit: I'm hoping to do this without caching, as it is a very simple need and I'm looking to keep the codebase lean and readable. Is it possible to store the partial as a string variable and then reference that twice?

Have you consider just using fragment caching (api.rubyonrails.org/classes/ActionController/Caching/…). If you are caching the same fragment, the cache call will stop the execution from occurring twice. — Rob Di Marco
– Rob Di Marco, Commented Jul 19, 2012 at 3:19
Hi Rob, see my edit above; I'm hoping to do this without caching if possible — Tyler
– Tyler, Commented Jul 19, 2012 at 5:44

nruth · Accepted Answer · 2019-01-19 18:28:49Z

8

<% content_for :example do %>
  <%= render :your_partial %>
<%end%>

then call <%= yield :example %> or <%= content_for :example %> wherever you want your partial called.

edited Jan 19, 2019 at 18:28

nruth

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answered Jul 19, 2012 at 5:58

Kyle C

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1 Comment

Tyler Over a year ago

Calling yield twice will not make the API call twice?

Thomas Fussell · Accepted Answer · 2012-07-19 14:33:43Z

6

One option would be to use fragment caching. After you wrap the partial with a cache block, the second call should show the cached version of the first. For example:

<% cache do %>
  <%= render(:partial => 'my_partial') %>
<% end %>

... later in the same view ...

<% cache do %>
  <%= render(:partial => 'my_partial') %>
<% end %>

To store the result of the render to a string, you could try the render_to_string method of AbstractController. The arguments are the same as for render.

partial_string = render_to_string(:partial => 'my_partial')

edited Jul 19, 2012 at 14:33

answered Jul 19, 2012 at 3:25

Thomas Fussell

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4 Comments

Tyler Over a year ago

I am familiar with fragment caching, but hoping to do this in a much simpler way (no need for sweepers, etc). The end HTML from the partial could be captured as a string variable and then simply rendered twice as such.

Thomas Fussell Over a year ago

I added another way if you want to take a look.

Tyler Over a year ago

This works in the controller [ render_to_string(:partial => 'my_partial', :locals => {:my_object => my_value}) ], but it takes about twice as long as simply making the API call twice and rendering twice. Any idea why?

Tyler Over a year ago

Just basing it on the rough 200 OK times for 5-10 requests in development mode. Render request is taking ~750ms, while render_to_string is taking ~1500ms. Is there additional overhead when invoking AbstractController?

nruth · Accepted Answer · 2019-01-19 14:55:03Z

I'm adding an answer to this old question because it topped Google for a search I just made.

There's another way to do this now (for quite a while), the capture helper.

<% reuse_my_partial = capture do %>
  <%= render partial: "your_partial" %>
<% end %>

<div class="visible-on-desktop"
  <%= reuse_my_partial %>
</div>

<div class="visible-on-mobile"
  <%= reuse_my_partial %>
</div>

This is simpler and slightly safer than using content_for because there is no global storage involved that something else might modify.

The rails docs linked to use instance @vars instead of local vars because they want it to be available to their layout template. That's a detail you do not need to worry about, because you're using it in the same template file.

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