🧭 Simplifying Deeply Nested Routes in Rails with shallow: true

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Simplifying Deeply Nested Routes in Rails with shallow: true

July 2, 2025

When building APIs or web applications using Ruby on Rails, one often encounters the challenge of managing deeply nested resources. While Rails’ routing DSL offers expressive ways to represent model relationships, deeply nested routes can result in unwieldy URLs, complicated controller logic, and a diminished developer experience.

To address this, Rails provides a powerful yet often underutilized option: shallow: true.

The Problem with Deep Nesting

By default, Rails generates full nested paths for all actions on child resources. While this ensures that relationships between entities (e.g., Album → Photo) are respected, it can quickly lead to verbose and redundant route structures:


/albums/12/photos/42/edit

From a RESTful perspective, such nesting is unnecessary for actions where the child resource can be uniquely identified by its own ID.

Enter shallow: true

Using the shallow: true option modifies the routing behavior such that only actions requiring context (usually index and create) remain nested. All other actions (show, edit, update, destroy) are generated as top-level routes using the child resource’s ID.


resources :albums do
  resources :photos, shallow: true
end

This configuration results in the following route structure:


GET /albums/:album_id/photos # index
POST /albums/:album_id/photos # create
GET /photos/:id # show
PATCH /photos/:id # update
DELETE /photos/:id # destroy
GET /photos/:id/edit # edit

This approach preserves the semantic clarity of resource relationships without sacrificing route simplicity.

Technical Advantages

Implementing shallow routes offers several tangible benefits:

Improved URL design : Cleaner and more intuitive endpoints (/photos/42 vs /albums/12/photos/42)
Decoupled controller logic : Controllers handling shallow routes can directly access the resource via params[:id], eliminating the need to load the parent model.
Scalability : Simplifies resource handling, particularly when child resources grow in complexity or evolve independently.
RESTful integrity : Aligns with the principle that each resource should be accessible via its canonical URI.

When Not to Use Shallow Routes

Shallow routing is not a one-size-fits-all solution. If a child resource cannot or should not exist independently of its parent (e.g., a Comment that always requires context of both Project and Task), enforcing full nesting might be desirable to ensure referential integrity and reduce the likelihood of orphaned access.

Applying shallow: true in Deep Hierarchies

Consider a more complex example:


resources :projects do
  resources :tasks, shallow: true do
    resources :comments, shallow: true
  end
end

This will generate routes that respect the hierarchical model structure but avoid unnecessary nesting in the final URLs, especially for lower-level resources like comments.

Conclusion

The shallow: true option exemplifies the Rails philosophy of developer happiness and convention over configuration. It balances clarity and maintainability, allowing developers to represent model relationships in a clean and practical way.

When applied judiciously, shallow routing can significantly reduce complexity in both routing definitions and controller logic, while preserving the structural integrity of your application’s domain.

Have you used shallow: true in your Rails projects? What benefits or tradeoffs did you encounter? I’d love to hear your insights.