Speed up rendering Rails pages with this gem.

render_async renders partials to your views asynchronously. This is done through adding Javascript code that does AJAX request to your controller which then renders your partial into a Rails view.

Workflow:

1. user visits a Rails page
2. AJAX request on the controller action
3. controller renders a partial
4. partials renders in the place where you put render_async helper

Javascript is injected into <%= content_for :render_async %> so you choose where to put it.

Add this line to your application's Gemfile:

gem 'render_async'

And then execute:

$ bundle install

1. Include render_async view helper somewhere in your views:

   # app/views/comments/show.html.erb
   
   <%= render_async comment_stats_path %>

2. Then create a route that will config/routes.rb

   # config/routes.rb
   
   get :comment_stats, :controller => :comments

3. Fill in the logic in your controller

   # app/controllers/comments_controller.rb
   
   def comment_stats
     @stats = Comment.get_stats
   
     render :partial => "comment_stats"
   end

4. Create a partial that will render

   # app/views/comments/_comment_stats.html.erb
   
   <div class="col-md-6">
     <%= @stats %>
   </div>

5. Add content_for in your base view file

   # application.html.erb
   
   <%= content_for :render_async %>

render_async takes two arguments, path and html_options.

• path is the AJAX-capable controller action you're looking to call via GET. e.g. comments_stats_path, posts_path, etc.
• html_options is an optional hash that gets passed to a rails javascript_tag, to drop html tags into the script element.

Example of utilizing html_options with a nonce:

<%= render_async users_path, nonce: 'lWaaV6eYicpt+oyOfcShYINsz0b70iR+Q1mohZqNaag=' %>

Rendered code in the view:

<div id="render_async_18b8a6cd161499117471">
</div>

<script nonce="lWaaV6eYicpt+oyOfcShYINsz0b70iR+Q1mohZqNaag=">
//<![CDATA[
  ...
//]]>
</script>

render_async can be called with a block that will act as a placeholder before your AJAX call finishes.

Example of passing in a block:

<%= render_async users_path do %>
  <h1>Users are loading...</h1>
<% end %>

Rendered code in the view:

<div id="render_async_14d7ac165d1505993721">
  <h1>Users are loading...</h1>
</div>

<script>
//<![CDATA[
  ...
//]]>
</script>

After AJAX is finished, placeholder will be replaced with the request's response.

render_async can receive :event_name option which will emit Javascript event after it's done with fetching and rendering request content to HTML.

This can be useful to have if you want to add some Javascript functionality after your partial is loaded through render_async.

Example of passing it to render_async:

<%= render_async users_path, :event_name => "users-loaded" %>

Rendered code in view:

<div id="render_async_04229e7abe1507987376">
</div>

<script>
//<![CDATA[
  ...
    document.dispatchEvent(new Event("users-loaded"));
  ...
//]]>
</script>

Then, in your JS, you could do something like this:

document.addEventListener("users-loaded", function() {
  console.log("Users have loaded!");
});

render_async can utilize view fragment caching to avoid extra AJAX calls.

In your views:

# app/views/comments/show.html.erb

# note 'render_async_cache' instead of standard 'render_async'
<%= render_async_cache comment_stats_path %>

# app/views/comments/_comment_stats.html.erb

<% cache render_async_cache_key(request.path), :skip_digest => true do %>
  <div class="col-md-6">
    <%= @stats %>
  </div>
<% end %>

• The first time the page renders, it will make the AJAX call.
• Any other times (until the cache expires), it will render from cache instantly, without making the AJAX call.
• You can expire cache simply by passing :expires_in in your view where you cache the partial

On Turbolinks applications, you may experience caching issues when navigating away from, and then back to, a page with a render_async call on it. This will likely show up as an empty div.

To resolve, tell turbolinks to reload your render_async call as follows:

  <%= render_async events_path, 'data-turbolinks-track': 'reload' %>

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

Bug reports and pull requests are welcome on GitHub at https://github.com/renderedtext/render_async.

The gem is available as open source under the terms of the MIT License.

Thanks goes to these wonderful people (emoji key):

Nikola Đuza 💬 🐛 💻 📖 💡 👀	Colin 💻 📖	Kasper Grubbe 💻	Sai Ram Kunala 📖	Josh Arnold 💻 📖	Elad Shahar 💻	Sasha 💻 📖

This project follows the all-contributors specification. Contributions of any kind welcome!