How to Use Member and Collection Routes in Ruby on Rails

In Ruby on Rails, use member routes to add custom actions that operate on a single resource item, and collection routes for actions that apply to the entire resource collection. Define them inside the resources block in config/routes.rb to create RESTful custom routes easily.

Syntax

Inside the resources block, use member to define routes that require an ID (operate on one item), and collection for routes that don't need an ID (operate on all items).

• member do: Defines routes like /resources/:id/action.
• collection do: Defines routes like /resources/action.
• Inside these blocks, use HTTP verbs like get, post, etc., to specify the action.

ruby

resources :photos do
  member do
    get 'preview'
  end

  collection do
    get 'search'
  end
end

Example

This example shows how to add a preview action for a single photo and a search action for all photos.

ruby

Rails.application.routes.draw do
  resources :photos do
    member do
      get 'preview'
    end

    collection do
      get 'search'
    end
  end
end

# Controller: app/controllers/photos_controller.rb
class PhotosController < ApplicationController
  def preview
    @photo = Photo.find(params[:id])
    render plain: "Previewing photo ##{@photo.id}"
  end

  def search
    render plain: "Searching all photos"
  end
end

Output

GET /photos/1/preview => "Previewing photo #1"
GET /photos/search => "Searching all photos"

Common Pitfalls

• Defining a member route but forgetting it needs an :id parameter causes routing errors.
• Using collection when the action requires an ID will fail because no ID is passed.
• Not specifying the HTTP verb inside member or collection blocks leads to unexpected routes.

ruby

resources :photos do
  # Wrong: 'preview' needs an ID, so it must be a member route
  collection do
    get 'preview'
  end

  # Right:
  member do
    get 'preview'
  end
end

Quick Reference

Route Type	URL Pattern	Purpose	Example
member	/photos/:id/action	Action on a single resource	GET /photos/1/preview
collection	/photos/action	Action on the whole collection	GET /photos/search

Key Takeaways

Use member routes for actions on individual resource items requiring an ID.

Use collection routes for actions on the entire resource collection without an ID.

Define these routes inside the resources block in config/routes.rb.

Always specify the HTTP verb (get, post, etc.) inside member or collection blocks.

Avoid mixing member and collection incorrectly to prevent routing errors.