What Are Reusable Code Blocks?

Reusable Code Blocks (called “Custom Code” in JCB) are named, context-aware entities that contain PHP or HTML code. Instead of writing the same logic in multiple templates or controller files, you can:

• Create a code block once via the JCB GUI.
• Reference it anywhere in your project using its unique key.
• Have it injected dynamically at compile time, respecting placeholders and environment.

Key Features

• 🔑 Named Reference Keys: Each reusable block is uniquely identified by a key (e.g., custom.user.validation), making it easy to reference.
• 🔄 Inject Anywhere: You can inject these code blocks into views, models, templates, controllers, or even inside other custom code blocks.
• 🧠 Dynamic Placeholder Support: Insert context-specific variables like {item.id}, {user.id}, {table}, {view} etc., which get replaced during compilation.
• 📦 PHP or HTML Compatible: Define business logic, HTML output, or mixed content. Both front-end and back-end environments are supported.
• 👁️‍🗨️ Visual Diff & Update Detection: JCB compares injected versions to originals and warns you if something has been manually changed, preserving the round-trip editing experience.
• 📍 Round-Trip Friendly: Changes injected into compiled files are preserved across rebuilds using insert/replace tags, making the system robust for iterative development.

Use Cases

• Shared validation logic across views
• Render repeated HTML elements like toolbars or status badges
• Common AJAX handlers or controller functions
• Role-checking logic injected into multiple places
• Layout segments like footers, titles, or custom buttons

How to Use

1. Go to Custom Code in JCB
2. Create a new code block and assign it a unique key
3. Define your logic (PHP or HTML)
4. Reference this key in any view/template using the injection system
5. Compile and view it auto-injected where expected

Smart Features

• Code blocks can be versioned and stored like other entities
• Detected during diff comparisons for override safety
• Support nesting (a custom code block can call another)

Why It Matters

• ✅ DRY Principle (Don’t Repeat Yourself): Write once, use anywhere. Greatly improves maintainability and avoids code duplication.
• ✅ Faster Prototyping: Once a block is defined, it can instantly be reused in other components or views.
• ✅ Cleaner Views and Templates: Avoid clutter by abstracting reusable logic out of the view and into structured code blocks.

Conclusion

Custom Code Entities in JCB are a developer’s shortcut to writing efficient, consistent, and maintainable Joomla extensions. They enable a modular development style while ensuring every piece of logic is reusable and traceable. Whether you're building complex workflows or simply want to DRY up your markup — universal reusable code blocks are an essential part of modern JCB development.

Summary

Reusable code blocks in Joomla Component Builder (JCB) allow you to define snippets of PHP or HTML once and inject them dynamically into multiple parts of your component. These code entities — known in JCB as Custom Code — are universal and logic-aware. They reduce duplication, improve maintainability, and ensure consistency across admin views, site views, templates, and more.