How to Use Partials in Rails: Syntax and Examples

In Rails, use render partial: 'partial_name' or simply render 'partial_name' to include reusable view snippets called partials. Partials help keep views clean by extracting repeated HTML into separate files prefixed with an underscore.

Syntax

Partials are small view templates stored in the app/views folder with filenames starting with an underscore (_). To include a partial in another view, use the render method.

• render 'partial_name': Renders the partial named _partial_name.html.erb from the current controller's view folder.
• render partial: 'partial_name': Explicit syntax for rendering the partial.
• render partial: 'folder/partial_name': Renders a partial from a subfolder.
• render partial: 'partial_name', locals: { key: value }: Passes local variables to the partial.

erb

<%= render 'shared/header' %>
<%= render partial: 'comments/comment', locals: { comment: @comment } %>

Example

This example shows how to create and use a partial to display a comment. The partial receives a local variable comment and displays its content.

erb

<!-- app/views/comments/_comment.html.erb -->
<p><strong><%= comment.author %>:</strong> <%= comment.body %></p>

<!-- app/views/comments/index.html.erb -->
<h2>Comments</h2>
<%= render partial: 'comment', collection: @comments %>

Output

<h2>Comments</h2>
<p><strong>Alice:</strong> Great post!</p>
<p><strong>Bob:</strong> Thanks for sharing.</p>

Common Pitfalls

• Forgetting the underscore (_) in the partial filename will cause Rails not to find the partial.
• Not passing required local variables to the partial can cause errors or missing data.
• Using render 'partial_name' without specifying the folder when the partial is in a different folder leads to missing partial errors.
• Confusing render partial: 'name' with rendering a full template; partials are meant for reusable snippets only.

erb

<!-- Wrong: missing underscore in filename -->
<!-- Filename: comment.html.erb instead of _comment.html.erb -->
<%= render 'comment' %>

<!-- Right: correct filename -->
<!-- Filename: _comment.html.erb -->
<%= render 'comment' %>

Quick Reference

Use these tips to work effectively with Rails partials:

• Partial filenames start with an underscore, e.g., _menu.html.erb.
• Use render 'partial_name' to include partials.
• Pass variables with locals: { key: value }.
• Use collection: to render a list of partials for an array.
• Keep partials focused on small reusable pieces of UI.

Key Takeaways

Partials are reusable view snippets stored with filenames starting with an underscore.

Use render 'partial_name' or render partial: 'partial_name' to include partials in views.

Pass data to partials using the locals option to keep them flexible.

Always name partial files with a leading underscore to avoid missing partial errors.

Use partials to keep your views clean and DRY by extracting repeated HTML.