Ruby on Rails Interview Questions and Answers

This section covers frequently asked Ruby on Rails interview questions.

1. What is Ruby on Rails?

Ruby on Rails is a popular server-side web application framework written in Ruby. It's known for its convention-over-configuration approach, making development faster and more efficient. It follows the Model-View-Controller (MVC) pattern.

2. Explain DRY in Rails.

DRY (Don't Repeat Yourself) is a fundamental principle in software development. It emphasizes writing concise, reusable code to avoid redundancy and improve maintainability.

3. Current Version of Ruby on Rails.

(The specific version number should be updated here to reflect the most current release.)

4. Explain CoC (Convention over Configuration) in Rails.

Convention over configuration means that Rails provides sensible defaults and conventions for how things should be structured. This reduces the amount of explicit configuration required, speeding up development.

5. Who Created Rails?

David Heinemeier Hansson (DHH) created Ruby on Rails.

6. Methods to Install Ruby on Rails.

  • Using rbenv (recommended)
  • Using rvm
  • From source code

7. Rails IDEs and Editors.

You can use various IDEs or text editors for Rails development, including:

  • TextMate
  • VS Code
  • IntelliJ IDEA
  • NetBeans
  • Eclipse
  • RubyMine

(Many other IDEs could also be listed here.)

8. Rails Scripts.

Rails provides command-line tools (scripts) for various tasks:

  • rails console
  • rails server (often uses WEBrick)
  • Generators (for creating models, controllers, etc.)
  • Migrations (for managing database schema changes)

9. Disadvantages of Ruby on Rails.

  • Can be challenging to work with multiple databases simultaneously.
  • Limited built-in support for certain database features (like foreign keys in some cases).
  • Less robust support for SOAP-based web services compared to other frameworks.

10. The super Function in Rails.

super calls the method from the parent (super) class. This is useful for extending methods while reusing the parent class's functionality.

11. Active Record in Rails.

Active Record is Rails' Object-Relational Mapper (ORM). It simplifies database interactions by mapping database tables to Ruby classes and database records to Ruby objects. This significantly reduces the amount of database-specific code you need to write.

12. Who Designed Active Record?

Active Record is based on a design pattern by Martin Fowler.

13. Models in Rails.

Models represent data and business logic. In Rails, they're typically Active Record classes that interact with the database.

14. Command to Create a Migration.

rails generate migration create_table_name

15. The defined? Operator.

defined? checks if a variable or method is defined.

16. Purpose of super.

super calls the method from the parent class, enabling code reuse and extension.

17. Syntax of each Iterator.

Syntax

collection.each do |variable|
  # Code to execute for each element
end

18. What are Hashes?

Hashes are key-value pairs, similar to dictionaries in other languages.

19. Creating Blocks.

Syntax

block_name { |variable|
  # Code within the block
}

20. Variable Naming Conventions.

Lowercase with underscores separating words (e.g., my_variable).

21. Procs vs. Blocks.

Procs are objects representing blocks of code. Blocks are code blocks passed to methods; they are not objects themselves.

22. Single vs. Double Quotes for Strings.

Single quotes prevent string interpolation (replacing variables within the string) and don't process escape sequences.

23. Rails Migrations.

Migrations manage database schema changes in a version-controlled way.

24. Creating a Controller.

rails generate controller controller_name

25. Views in Rails.

Views are responsible for presenting data to the user. They're typically ERB (Embedded Ruby) templates.

26. Controllers in Rails.

Controllers handle user requests, interact with models, and select the appropriate views to render.

27. RVM (Ruby Version Manager) in Rails.

RVM manages different Ruby versions and environments on your system.

28. Gemsets in Rails.

Gemsets allow you to isolate gems (libraries) for different projects, avoiding conflicts between versions.

29. Updating RVM.

rvm get head

30. Bundler in Rails.

Bundler manages dependencies (gems) for your Rails application, ensuring consistent environments.

31. Why Use Migrations in Rails?

Migrations provide a structured, version-controlled way to modify your database schema, making it easier to track changes and manage database updates.

32. Running Migrations.

rake db:migrate

33. How Rails Router Works.

The router maps URLs to controller actions and generates URLs from routes.

34. REST in Rails Routes.

RESTful routing uses HTTP methods (GET, POST, PUT, DELETE) to define actions on resources.

35. Nested Scaffolding Features.

Nested scaffolding generates nested resources with associated models and views, simplifying the creation of complex relationships within your application.

36. Creating Rails Layout HTTP Responses.

  • render: Creates a full response.
  • redirect_to: Redirects to another URL.
  • head: Sends only headers.

37. Importance of yield in Rails Layouts.

yield in a Rails layout defines where the content from the view (rendered by a controller action) should be inserted.

38. Types of Filters in Rails.

  • Before filters
  • After filters
  • Around filters

39. Protecting Filter Methods in Rails.

Use access control modifiers (public, protected, private) to control which parts of your application can access methods.

40. Testing in Rails.

Rails uses Test::Unit (and other testing frameworks like RSpec) for testing. Types of tests include unit, integration, and functional tests.

41. Rails Caching Levels.

Rails caching improves performance by storing frequently accessed data. It works at three levels:

  • Page caching: Caches entire pages.
  • Action caching: Caches the results of controller actions.
  • Fragment caching: Caches specific parts (fragments) of a page.

42. Rails Validations.

Validations in Rails (using Active Record) define rules to ensure data integrity. They prevent invalid data from being saved to the database.

43. valid? and invalid? in Rails.

  • valid?: Returns true if a model's data is valid according to its validations, false otherwise.
  • invalid?: The opposite of valid?.

44. Unobtrusive JavaScript in Rails.

(This would need a more detailed explanation of unobtrusive JavaScript techniques within the context of Rails applications.)

45. Symbol Garbage Collector.

The symbol garbage collector reclaims unused symbols. Symbols are often used as keys in hashes; this helps optimize memory usage and security.

46. Action Cable in Rails.

Action Cable provides real-time functionality to Rails applications using WebSockets. It simplifies building features like chat, live updates, etc.

47. Ruby on Rails IDEs.

Several IDEs support Rails development:

  • TextMate (Mac): A popular text editor with extensions (bundles).
  • VS Code: A versatile and highly customizable code editor with excellent Rails support.
  • IntelliJ IDEA: A commercial IDE with strong Rails features.
  • NetBeans: An IDE with Rails support.
  • Eclipse (with RadRails plugin): A widely used IDE that can be extended for Rails development.
  • Heroku: A cloud-based platform that also provides online development capabilities.
  • Aptana Studio: An Eclipse-based IDE for web development.
  • RubyMine: A powerful IDE specifically designed for Ruby and Rails development.

48. Rails Console.

The Rails console is an interactive command-line tool that lets you interact directly with your Rails application's environment, models, and data.

49. Generators in Ruby on Rails.

Rails generators automatically create files (models, controllers, views, migrations) for new features, speeding up development.

50. WEBrick Web Server.

WEBrick is a simple, pure-Ruby web server often used for development. Rails automatically uses it unless another server (like Puma or Thin) is specified.