API versioning in Ruby on Rails - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is API versioning in Rails?

API versioning is a way to manage changes in your API over time by creating different versions. This helps keep old clients working while allowing new features in newer versions.

beginner

Name two common ways to version an API in Rails.

1. Using URL path versioning (e.g., /api/v1/)
2. Using HTTP headers to specify the version

intermediate

How do you set up URL path versioning in Rails routes?

You add a version segment in your routes like:
namespace :api do
namespace :v1 do
resources :posts
end
end
This creates routes under /api/v1/posts.

beginner

Why is API versioning important for backward compatibility?

It allows old clients to keep working with the API without breaking, even when new features or changes are added in newer versions.

intermediate

What is a downside of using URL path versioning?

It can lead to duplicated code and more maintenance because each version might need separate controllers and views.

Which of these is a common way to version an API in Rails?

A Using URL path segments like /api/v1/

B Changing the database schema for each version

C Using CSS classes to mark versions

D Renaming the Rails app folder

API versioning commonly uses URL path segments or HTTP headers, not database schema changes or CSS.

What does the namespace :v1 do in Rails routes?

A Updates the Rails version

B Changes the database version

C Groups routes under /v1/ path

D Creates a new model

Namespace :v1 groups routes under the /v1/ URL path, helping organize API versions.

Why might you use HTTP headers for API versioning instead of URL paths?

A Because headers are easier to see in the browser

B To keep URLs clean and separate version info

C To avoid using JSON

D To speed up the server

Using HTTP headers keeps URLs clean and moves version info to request headers.

What is a risk if you don’t version your API?

A Old clients may break when API changes

B The app will run faster

C You get more users

D The database will auto-update

Without versioning, changes can break old clients relying on previous API behavior.

In Rails, where do you usually put versioned API controllers?

A In the config folder

B In the root app/controllers folder only

C In the assets folder

D In folders matching the version, like app/controllers/api/v1/

Versioned API controllers are organized in folders by version to keep code clear and separate.

Explain how you would add versioning to a Rails API using URL paths.

Think about how URLs and folders help organize versions.

Why is API versioning important when you update your API?

Consider what happens if you change the API without warning.

Practice

1. What is the main purpose of API versioning in a Rails application?

easy

A. To change the database schema automatically

B. To allow updates without breaking existing API users

C. To speed up database queries

D. To improve the UI design of the application

Solution

1. Step 1: Understand API versioning concept

   API versioning allows developers to release new API features or changes without affecting users who rely on older versions.

2. Step 2: Identify the main benefit

   This prevents breaking changes and keeps old clients working while new clients can use updated features.

3. Final Answer:

   To allow updates without breaking existing API users -> Option B

4. Quick Check:

   API versioning = safe updates [OK]

Hint: API versioning = safe updates without breaking old clients [OK]

Common Mistakes:

• Thinking it speeds up database queries
• Confusing with UI improvements
• Assuming it changes database schema automatically

2. Which of the following is the correct way to define API versioning in Rails routes using namespaces?

easy

A. version :v1 do
resources :users
end

B. scope :v1 do
resources :users
end

C. namespace :v1 do
resources :users
end

D. api_version :v1 do
resources :users
end

Solution

1. Step 1: Recall Rails routing syntax for versioning

   Rails uses the namespace method to group routes under a version folder like v1.

2. Step 2: Check each option

   Only namespace :v1 do ... end is valid Rails syntax for versioning routes.

3. Final Answer:

   namespace :v1 do resources :users end -> Option C

4. Quick Check:

   Rails versioning uses namespace [OK]

Hint: Use namespace for version folders in routes [OK]

Common Mistakes:

• Using non-existent 'version' or 'api_version' methods
• Using scope without path or module options
• Confusing namespace with scope

3. Given this routes setup in Rails:

namespace :v1 do
  get 'status', to: 'health#show'
end
namespace :v2 do
  get 'status', to: 'health#show'
end

What will GET /v2/status call?

medium

A. The show action in HealthController inside V2 module

B. The show action in the main HealthController without module

C. A routing error because v2 is not defined

D. The show action in HealthController inside V1 module

Solution

1. Step 1: Understand namespace routing effect

   Each namespace creates a module scope. So v2 routes call controllers inside V2:: module.

2. Step 2: Match the route to controller

   GET /v2/status calls V2::HealthController#show, not the v1 or main controller.

3. Final Answer:

   The show action in HealthController inside V2 module -> Option A

4. Quick Check:

   Namespace v2 routes call V2 controllers [OK]

Hint: Namespace URL matches controller module [OK]

Common Mistakes:

• Assuming v2 calls v1 controller
• Thinking it causes routing error
• Ignoring module scoping in namespaces

4. You have this routes file snippet:

namespace :v1 do
  resources :products
end

namespace :v1 do
  resources :orders
end

What is the problem with this code?

medium

A. You must use scope instead of namespace for versioning

B. Rails does not allow multiple namespaces with the same name

C. Resources inside namespaces must be singular, not plural

D. Duplicate namespace declarations can be merged into one block

Solution

1. Step 1: Analyze namespace usage

   Rails allows multiple namespace blocks with the same name but it's better style to merge them.

2. Step 2: Identify best practice

   Merging namespace :v1 blocks into one improves readability and avoids confusion.

3. Final Answer:

   Duplicate namespace declarations can be merged into one block -> Option D

4. Quick Check:

   Merge same namespaces for clarity [OK]

Hint: Merge same namespaces into one block [OK]

Common Mistakes:

• Thinking Rails forbids multiple same namespaces
• Using singular resources incorrectly
• Confusing namespace with scope

5. You want to support two API versions in your Rails app: v1 and v2. v1 returns user data with name only, but v2 adds email. How should you organize your controllers to handle this cleanly?

hard

A. Create separate controllers under app/controllers/v1/users_controller.rb and app/controllers/v2/users_controller.rb with different responses

B. Use a single controller and check version in each action to decide response

C. Put all logic in the model and use one controller for both versions

D. Use middleware to rewrite responses after controller runs

Solution

1. Step 1: Understand version separation best practice

   Separate controllers per version keep code clean and maintainable, avoiding complex conditionals.

2. Step 2: Apply Rails versioning pattern

   Place controllers in versioned folders like v1/users_controller.rb and v2/users_controller.rb to handle different responses.

3. Final Answer:

   Create separate controllers under app/controllers/v1/users_controller.rb and app/controllers/v2/users_controller.rb with different responses -> Option A

4. Quick Check:

   Separate controllers per version = clean code [OK]

Hint: Use separate controllers per version folder [OK]

Common Mistakes:

• Using one controller with many version checks
• Putting version logic in models
• Trying to rewrite responses with middleware