Ruby Interview Study Guide

• Concepts
  • Sidekiq / Jobs
  • ActiveRecord Relations
• Questions
  • Ruby General
    • Describe the difference between class and instance variables?
      • Class variables are shared by all instances of a class, while instance variables belong to particular instances.

class MyClass
  @@myClassVariable = 'MyClass'
  @myInstanceVariable = 'foo'
end

• Everything (amost) in an object in Ruby. Explain?
  • everything in Ruby is a subclass of the Class class, including nil. The parts of the language that aren't objects are blocks, methods, and conditional statements
• There are three ways to invoke a method in Ruby, can you tell me at least two?
  • dot operator, Object#send, .method(:foo) call.
• Explain this ruby idiom: a ||= b
  • This expression assignments the value of b to a if a is falsy (nil false or undefined).
• What happens when you call a method in Ruby?
• How do you declare a constructor in a ruby class?

class MyClass
  def initialize
    # my constructor
  end

• When do you use self in Ruby?
• What is the difference between a proc and a lmabda?
• What is the splat operator?
• What is the difference between include and extend?
• What is the difference between a class and a module?
• What is the difference between each, select, map, and collect?
  • each is the equivalent of JS's "foreach" and returns the array unaltered. collect is like JS's map, it returns an altered array. map is an alias for collect. select works like filter.
• Rails General
  • What are some of your favorite ruby gems, besides Ruby on Rails?
    • Devise, ActiveAdmin, RSpec
  • What is a Rails engine?
  • What is the purpose of a rakefile?
  • What is a rails migration?
• Workers / Jobs
  • What is ActiveJob? When Should we use it?
    • A job is a bit of work that is assigned to work in one of many queueing systems.
  • What are some frameworks you have used for background jobs?
    • Sidekiq
• Controllers / Routing
  • Describe the CRUD verbs and actions
    • index -> GET
    • new -> GET
    • create -> POST
    • show -> GET
    • edit -> GET
    • update -> PATCH/PUT
    • delete -> DELETE
  • difference between PUT and PATCH?
    • PUT requests should supply an updated version of the resource. A PATCH request supplies
  • Why should you avoid fat controllers?
    • tight coupling makes applications harder to reason about and debug. Tighter coupling leads to less flexible code, which makes adjusting to changing requirements. It also is a poor seperation of concerns; the single responsibility of a controller is to a request and generate a response. Also, controllers tend to be harder to test.
  • What does the 'resources' method do, and how does it work?
  • How do you set up a single route without using resources?
  • You’re setting up the routes for a website that displays information on different genres of music. Using the URL path /music/ as an example, create a route that uses a single controller action for each genre of music with the actual music genre passed into the controller action as a parameter. The valid music genres are as follows: classical, rock, house, country, hip_hop, and rnb. All other genres should generate a 404 status code.
• Active Record
  • Describe the types of associations in Active Record, and when to use each?
  • What are scopes? How should you use them?
  • What's the difference between count, length, and size?
  • What are callbacks, and when would you use them?
  • What are the downsides of callbacks?
  • What's the difference between delete and destroy?
  • What is the difference between find find_by and where in ActiveRecord?
  • What are some ways to optimize ActiveRecord performance?
• Software engineering
  • How do you approach refactoring?
  • How to tackle legacy code / code smells?
• Software Arcitecture
  • "What does "favor composition over inheritance" mean, and why is it important? "
  • Why should you avoid fat models?
  • How can you avoid fat models?
  • How can you avoid fat controllers?
  • Explain Value, Service, Form, View, Query, and Policy Objects techniques Ruby on Rails Design Patterns
  • What are some rails design patterns you've used?
    • Query pattern for the task queue.
    • Domain objects for concerns like 3rd party integrations (Stripe)
    • Serializer pattern for JSON APIs (does this count as a pattern?)
  • How have you implemented authorization in the past?
    • Devise, Pundit
• System Arcitecture
  • "How would design an API? "
  • "What are the pros and cons of monolithic vs microservice architectures? "
• Automated Testing
  • What is unit testing?
  • What is your testing strategy?
  • What are your favorite tools for writing unit tests?
  • What are your favorite tools for writing feature tests?