Mastering ERB in Ruby on Rails: Why It’s Still a Developer Favorite

January 30, 2025

If you’ve worked with Ruby on Rails, you’ve likely encountered ERB (Embedded Ruby)—the quiet powerhouse behind dynamic, maintainable Rails views. While newer templating engines like HAML or Slim often steal the spotlight, ERB remains a staple for its simplicity, flexibility, and deep Rails integration. Let’s explore why ERB deserves more love and how to wield it effectively.

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What Makes ERB Special?

ERB lets you embed Ruby directly into HTML (or any text format), acting as a bridge between logic and presentation. Here’s why it shines:

1️⃣ HTML-First Approach: ERB doesn’t force you to learn a new syntax—just write HTML and sprinkle Ruby where needed. This makes it accessible to frontend developers and minimizes context-switching.

2️⃣ Seamless Rails Integration:

Direct access to instance variables (like @user) from controllers.
Built-in view helpers (e.g., link_to, form_with) for clean, semantic code.
Partials and layouts to DRY up repetitive UI components.

3️⃣ Security by Default: ERB auto-escapes HTML to guard against XSS attacks. Need raw HTML? Use raw or sanitize for controlled exceptions.

Advanced ERB Techniques You Should Know

Want to level up? Try these pro tips:

🔹 Whitespace Control: Trim unwanted newlines with <% -%> to keep your generated HTML clean:

<% @posts.each do |post| -%>  
  <h2><%= post.title %></h2>  
<% end -%>

🔹 Content Capture: Use content_for to inject dynamic sections (e.g., page-specific meta tags) into layouts:

<% content_for :meta_description do %>  
  <%= truncate(@post.summary, length: 150) %>  
<% end %>

🔹 Caching: Speed up rendering with fragment caching:

<% cache("user-header-#{@user.id}") do %>  
  <%= render 'shared/user_header', user: @user %>  
<% end %>

When to Choose ERB Over Alternatives

While HAML/Slim offer concise syntax, ERB wins in scenarios like:

Legacy Projects: Many Rails codebases still rely on ERB.
Team Familiarity: Less learning curve for developers comfortable with HTML.
Complex Views: Need to mix HTML with third-party JS/CSS? ERB’s flexibility shines.

Best Practices for Clean ERB Code

🚫 Avoid Business Logic: Keep conditionals/loops simple; delegate complex logic to helpers or decorators.
✅ Use Partials Wisely: Break views into reusable components (e.g., _navbar.html.erb).
🔒 Sanitize User Input: Always use sanitize when rendering untrusted content.

Final Thoughts

ERB’s strength lies in its simplicity and Rails-native design. Whether you’re building a startup MVP or maintaining an enterprise app, understanding ERB unlocks faster iteration and cleaner templates.

Your Turn: How do you structure ERB templates in large Rails apps? Any favorite tricks? Let’s discuss in the comments! 👇