Rails what is the difference between content_for and yield?

Question

For example: content_for(:stuff) vs yield :stuff

I know they are implemented slightly differently, but is there any real functionality difference?

Is there a generally accepted best practice?

Answer 1

yield is how you specify where your content areas is going to go within a layout. You might have something like this:

<div>
  <h1> This is the wrapper!</h1>
  <%= yield :my_content %>
</div>

content_for is how you specify which content is going to be rendered into which content area. You might have something like this:

<% content_for :my_content do %>
  This is the content.
<% end %>

The result would be

<div>
  <h1> This is the wrapper!</h1>
  This is the content.
</div>

They are opposite ends of the rendering process, with yield specifying where content goes, and content_for specifying what the actual content is.

Is there a generally accepted best practice?

The best practice is to use yield in your layouts, and content_for in your views. There is a special second use for content_for, where you give it no block and it returns the previously rendered content. This is primarily for use in helper methods where yield cannot work. Within your views, the best practice is to stick to yield :my_content to recall the content, and content_for :my_content do...end to render the content.

Answer 2

Calling #content_for stores a block of markup in an identifier for later use. In order to access this stored content in other templates, helper modules or the layout, you would pass the identifier as an argument to content_for. yield can still be used to retrieve the stored content, but calling yield doesn't work in helper modules, while content_for does....more: http://api.rubyonrails.org/classes/ActionView/Helpers/CaptureHelper.html#method-i-content_for