RailsHow-ToBeginner · 3 min read

How to Use content_for in Rails: Syntax and Examples

In Rails, content_for lets you define named content blocks in views that you can render later in layouts using yield. Use content_for :name do ... end to set content and yield :name in the layout to display it.

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Syntax

The content_for method defines a named content block inside a view. You write content_for :block_name do ... end to capture content. In the layout, use yield :block_name to render that content where you want it.

This helps you insert specific content like scripts, styles, or page titles from views into the layout.

erb

<%= content_for :sidebar do %>
  <p>This is sidebar content.</p>
<% end %>

<!-- In layout file -->
<%= yield :sidebar %>

Output

<p>This is sidebar content.</p>

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Example

This example shows how to set a page title and a sidebar content in a view, then render them in the layout.

erb

<!-- app/views/articles/show.html.erb -->
<% content_for :title do %>
  Article Details
<% end %>

<% content_for :sidebar do %>
  <p>Related Articles</p>
<% end %>

<h1>Article Content Here</h1>

<!-- app/views/layouts/application.html.erb -->
<html>
<head>
  <title><%= yield(:title) || "Default Title" %></title>
</head>
<body>
  <div class="sidebar">
    <%= yield :sidebar %>
  </div>
  <div class="main">
    <%= yield %>
  </div>
</body>
</html>

Output

<html> <head> <title>Article Details</title> </head> <body> <div class="sidebar"> <p>Related Articles</p> </div> <div class="main"> <h1>Article Content Here</h1> </div> </body> </html>

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Common Pitfalls

Forgetting to use yield :block_name in the layout means the content won't show.
Using content_for without a block or with incorrect syntax causes errors.
Trying to use content_for outside views (like controllers) won't work.
Overwriting content_for blocks unintentionally by calling it multiple times with the same name replaces previous content.

erb

<!-- Wrong: no yield in layout, content_for block won't display -->
<% content_for :footer do %>
  <p>Footer info</p>
<% end %>

<!-- layout missing: <%= yield :footer %> -->

<!-- Right: add yield in layout -->
<%= yield :footer %>

📊

Quick Reference

content_for usage:

content_for :name do ... end - Define content block named :name.
yield :name - Render the named content block in layout.
Use for titles, scripts, styles, sidebars, or any layout-specific content.

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Key Takeaways

Use content_for :name do ... end in views to define content blocks.

Render these blocks in layouts with yield :name to insert content.

Always ensure the layout includes yield :name or content won't appear.

Avoid overwriting content_for blocks unintentionally by calling them multiple times with the same name.

content_for works only inside views, not in controllers or helpers.