API versioning in Ruby on Rails - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

How does Rails route to different API versions?

Given a Rails API with versioning using namespace, what will be the response when calling GET /api/v2/products if only v1 namespace has a ProductsController?

Ruby on Rails

Rails.application.routes.draw do
  namespace :api do
    namespace :v1 do
      resources :products, only: [:index]
    end
    namespace :v2 do
      # No products controller defined here
    end
  end
end

A 404 Not Found error because v2/products route is not defined

B Returns the product list from v1/products controller

C Redirects automatically to v1/products endpoint

D 500 Internal Server Error due to missing controller

💡 Hint

Think about how Rails matches routes and controllers inside namespaces.

Rails routes are matched exactly. Since v2 namespace has no products controller or route, calling /api/v2/products results in 404 Not Found.

📝 Syntax

intermediate

Correct syntax for versioning with Accept header in Rails

Which option correctly configures Rails to use API versioning via the Accept header with version 'v1'?

A

class Api::BaseController < ActionController::API
  before_action :check_version

  private
  def check_version
    render status: 406 unless request.headers['Accept'] == 'application/json; version=1'
  end
end

B

class Api::BaseController < ActionController::API
  before_action :check_version

  private
  def check_version
    render status: 406 unless request.headers['Accept']&.include?('application/vnd.myapp.v1+json')
  end
end

C

class Api::BaseController < ActionController::API
  before_action :check_version

  private
  def check_version
    render status: 406 unless request.headers['Content-Type'] == 'application/vnd.myapp.v1+json'
  end
end

D

class Api::BaseController < ActionController::API
  before_action :check_version

  private
  def check_version
    render status: 406 unless request.headers['Accept-Version'] == 'v1'
  end
end

💡 Hint

The Accept header is used to specify the media type and version.

Option B correctly checks if the Accept header includes the custom media type with version 'v1'. Other options check wrong headers or content types.

❓ state_output

advanced

What is the response when version is missing in header?

In a Rails API that requires versioning via Accept header, what response code will the client get if the Accept header is missing?

Ruby on Rails

class Api::BaseController < ActionController::API
  before_action :check_version

  private
  def check_version
    unless request.headers['Accept']&.include?('application/vnd.myapp.v1+json')
      render json: { error: 'API version missing or unsupported' }, status: :not_acceptable
    end
  end
end

A 406 Not Acceptable with error message

B 200 OK with default version response

C 400 Bad Request with no message

D 500 Internal Server Error due to missing header

💡 Hint

Check the status code used in the render call.

The controller explicitly renders a 406 Not Acceptable status when the Accept header does not include the required version string.

🔧 Debug

advanced

Why does this versioned API controller not respond correctly?

Given this controller, why does the API always respond with 404 Not Found when requesting /api/v1/users?

Ruby on Rails

module Api
  module V1
    class UsersController < ApplicationController
      def index
        render json: { users: [] }
      end
    end
  end
end

Rails.application.routes.draw do
  namespace :api do
    namespace :v1 do
      get 'users', to: 'users#index'
    end
  end
end

A The controller inherits from ApplicationController instead of ActionController::API

B The routes use get instead of resources, causing routing failure

C The controller is namespaced but the file is not placed in the correct folder

D The render json syntax is incorrect and causes failure

💡 Hint

Rails expects controller files to be in folders matching their module namespaces.

If the controller file is not in app/controllers/api/v1/users_controller.rb, Rails will not find it and return 404.

🧠 Conceptual

expert

What is the main advantage of using URL path versioning over header versioning in Rails APIs?

Consider two common API versioning strategies in Rails: using URL path segments (e.g., /api/v1/) and using custom Accept headers. What is the main advantage of URL path versioning?

A It automatically updates clients to the latest API version without changes

B It allows more flexible version negotiation based on media types

C It reduces the number of routes needed in the Rails router

D It is easier for clients and browsers to test and cache because the version is visible in the URL

💡 Hint

Think about how URLs are used in browsers and caching systems.

URL path versioning makes the API version explicit in the URL, which helps with testing, bookmarking, and caching. Header versioning requires clients to set headers correctly.