RailsHow-ToBeginner · 3 min read

How to Use Nested Routes in Rails: Syntax and Examples

In Rails, you use nested routes by placing one resource block inside another in the config/routes.rb file. This creates URLs that reflect the parent-child relationship, like /parents/:parent_id/children/:id, helping organize related resources clearly.

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Syntax

Nested routes are defined by placing a resources block inside another resources block in config/routes.rb. The outer resource is the parent, and the inner resource is the child. This creates URLs that include the parent's ID, showing the relationship.

resources :parents defines routes for the parent resource.
Inside it, resources :children defines routes for the child resource nested under the parent.
The URL pattern becomes /parents/:parent_id/children/:id.

ruby

Rails.application.routes.draw do
  resources :parents do
    resources :children
  end
end

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Example

This example shows nested routes for articles and their comments. Comments belong to articles, so their routes are nested. This creates URLs like /articles/1/comments/5 to access comment 5 of article 1.

ruby

Rails.application.routes.draw do
  resources :articles do
    resources :comments
  end
end

Output

Prefix Verb URI Pattern Controller#Action article_comments GET /articles/:article_id/comments(.:format) comments#index POST /articles/:article_id/comments(.:format) comments#create new_article_comment GET /articles/:article_id/comments/new(.:format) comments#new edit_article_comment GET /articles/:article_id/comments/:id/edit(.:format) comments#edit article_comment GET /articles/:article_id/comments/:id(.:format) comments#show PATCH /articles/:article_id/comments/:id(.:format) comments#update PUT /articles/:article_id/comments/:id(.:format) comments#update DELETE /articles/:article_id/comments/:id(.:format) comments#destroy articles GET /articles(.:format) articles#index POST /articles(.:format) articles#create new_article GET /articles/new(.:format) articles#new edit_article GET /articles/:id/edit(.:format) articles#edit article GET /articles/:id(.:format) articles#show PATCH /articles/:id(.:format) articles#update PUT /articles/:id(.:format) articles#update DELETE /articles/:id(.:format) articles#destroy

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Common Pitfalls

Common mistakes when using nested routes include:

Over-nesting resources, which makes URLs long and complex.
Not passing the parent resource ID in controller actions, causing errors.
Using shallow nesting incorrectly, which can confuse URL helpers.

Always keep nesting to 1 or 2 levels deep for clarity and maintainability.

ruby

Rails.application.routes.draw do
  # Wrong: too deep nesting
  resources :countries do
    resources :cities do
      resources :streets
    end
  end

  # Right: shallow nesting for streets
  resources :countries do
    resources :cities do
      resources :streets, shallow: true
    end
  end
end

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Quick Reference

Tips for nested routes in Rails:

Use resources inside another resources to nest.
Limit nesting depth to 1 or 2 levels.
Use shallow: true to simplify nested routes for child resources.
Access parent IDs in controllers via params[:parent_id].
Use URL helpers like parent_child_path(parent, child) for links.

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Key Takeaways

Define nested routes by placing one resources block inside another in config/routes.rb.

Nested routes create URLs that reflect parent-child relationships, like /parents/:parent_id/children/:id.

Avoid deep nesting to keep URLs simple and maintainable.

Use shallow nesting to reduce URL complexity for deeply nested resources.

Access parent resource IDs in controllers via params[:parent_id] to link related data.