36 Fundamental Ruby Interview Questions You Must Ask

36 Fundamental Ruby Interview Questions

Ruby is one of the most popular programming languages in the world. In fact, it’s growing faster than any other language. As a result, there are many job opportunities for Ruby programmers but finding a qualified candidate can be tough.

To ensure you hired the best Ruby programmers, we compiled this list of 36 Ruby interview questions you must ask.

It can be difficult to find good applicants if you don’t know what you’re looking for or which questions to ask during an interview. These cleverly crafted interview questions will help you filter out candidates and hire only those with true potential.

Candidates will typically give you a range of responses to these questions, but there’s usually one that stands out.

For example, if you ask them what a “string interpolation” is and they reply with: “It means I can put variables directly in my string.” You know they’ve got the basics of Ruby down pat!

But, keep in mind that a Senior programmer should be able to answer all of the questions. Junior programmers might be able to answer some questions correctly but probably won’t cover everything.

Ruby Interview Questions You Must Ask

1. What is Ruby on Rails?

This question is intended to test understanding of what Ruby on Rails is, and if they know the basics.

2. Why is Ruby called a language of flexibility?

This is one of the more vague questions on the list, but it’s a good way to see if they have any knowledge about Ruby.

3. What are some benefits of using Ruby?

Benefits of using Ruby are:

  • It’s a Rapid Application Development (RAD) language, meaning you can quickly write code and get results without having to go through all the steps other languages require
  • It is an object-oriented programming language which makes for very clean code because classes allow us to group methods together with their data in one place so they don’t have to be repeated throughout your program
  • Ruby has builtin libraries that provide common functionality such as basic string operations or number-crunching functions–so programmers spend less time coding repetitive tasks and more time on what differentiates their application from others

4. List some features of Ruby?

Ruby has many features. Some of them are listed below.

  • Garbage Collection
  • Dynamic typing
  • Object-oriented
  • Flexible
  • Keyword arguments

5. Explain some differences between Ruby and Python?

Ruby and Python are both popular programming languages. In simple terms, Ruby is a dynamic language while Python is static. Dynamic languages use runtime binding when necessary to resolve the reference to an object or method call whereas static languages have pre-compiled bindings that are used in compilation time.

6. What are some common mistakes developers make when using Ruby?

When coming in as an outsider or new hire into an existing team of devs working on Ruby projects without enough time allotted for learning what they need/know before joining up. It happens often because senior-level engineers take comfort in knowing their teammates know exactly what they’re doing and don’t bother explaining things every day – which can be frustrating if you’ve been asked to jump onto the project mid-stride!

7. What is an example of a dynamic language?

An example of a dynamic programming language is Ruby, whereas C++ is a static programming language. Static languages use pre-compiled bindings that are used in compilation time, where the code executes as it’s written and does not need to be interpreted at run time by an interpreter or other program; while with dynamic languages, the bindings are not compiled until run time and it is then interpreted.

In-Depth Technical Interview Questions

8. What advantages does Ruby have over Java?

Ruby has many more features than Java such as being object-oriented, flexible, and having garbage collection built-in. Additionally, the syntax for declaring variables in ruby is much simpler than that found in java with no static types to contend with. This makes it easier to learn Ruby from scratch while also making it faster to type despite there not being any compile-time error checking (unless you use some type-checking tools). There’s also less burden on managing memory because objects can be created dynamically during runtime which means programs don’t need to know how much memory is available at compile time.

9. What are the advantages of Rails relative to other web development platforms?

The advantage of Rails over PHP, ASP, and Django (to name a few) would be that Ruby on rails takes care of all the server-side processing as well which means programmers can spend their time building out interfaces with less coding needed for each page request. In addition, there are more standardized practices in ruby so developers have little confusion when coming onto an existing project while working together. Besides these points, I think we could talk about this question much longer than 30 minutes!

10. Why is Ruby on Rails preferred over Python for web development?

Ruby is a more “batteries included” language than Python. It includes things like blocks (which allow you to do something when an exception occurs), built-in testing frameworks, automatic memory management with garbage collection, etc. This makes it much easier to get started with ruby than python because less work has to be done before getting your app up and running!

11. How does Ruby differ from Python or Perl? What should you know before choosing one language over another?

It depends on what your goal is – if it’s to work with a language that’s more popular, then Python is probably your best bet. If it’s for building small-to-large applications and maintainability is important, I would say Ruby on Rails is the way to go.

12. What are class libraries in Ruby?

In Ruby, class libraries are modules that can be reused by other classes. This is very important in the language because it allows developers to build on top of what’s already been created and save a lot of time coding from scratch.

Ruby class libraries contain a variety of domain-specific functionality, such as slugging and parsing.

13. What are some operators used in Ruby?

Some operators used in Ruby are Unary operator, Arithmetic operator, Bitwise operator, Logical operator, and Ternary operator. These operators work the same as they do in mathematics except you can only use them with two operands at a time. One caveat to watch out for is that there’s no operator precedence — so be sure to group your operations properly!

14. What is the difference between a regular expression and string matching?

Regular expressions are much more flexible than string matching. Regular expressions can match patterns, like “a word followed by another word” or “any alphabetical character.” String matches only find an exact sequence of characters, like “cat,” but won’t include words with nearby letters that form no pattern, such as ‘bat’.

15. What is RubyGems in Ruby programming language?

RubyGems is a package manager for Ruby. It’s the equivalent of Node Package Manager (npm) in JavaScript or pip install –user on Python and it can be used to manage gem dependencies as well as create executables that include those gems like Rails, Sinatra, etc.

16. What are Ruby variables?

Ruby variables hold data that can be used later in the program.

17. What are Ruby keywords?

Ruby is a highly dynamic, expressive language and everything can be reassigned to something else. We call these “keywords” or reserved words that cannot change their meaning from what they were originally defined as in the programming context of Ruby syntax:

18. How does one convert an integer to binary string using Ruby?

The following example converts an integer into its binary equivalent with help from Fixnum class’s hex method: num = 12345 #=> 43211211111i (Fixnum) num.hex #=> “0x123459e789b2359cbb49a27dcef886fe90abcdba”

19. What is the difference between nil and false in Ruby?

Nil is a “nothing” value. It’s used to represent the absence of objects and values that have not been set, or when something has gone wrong with an operation like dividing by zero, such as:

#nil_variable = nil (symbol) puts num / 0

puts 11/0

In the case where there are no parentheses following true in your Ruby script, it will be converted into false automatically if you are using Ruby version less than v.v for example:

true || do_something() #=> false (boolean)

20. Explain Ruby data types.

Ruby data types represent different kinds of values. When you have a string, like “Cody”, that’s an instance of the String data type.

21. What are the different data types in Ruby?

There are six data types in Ruby: numbers, strings, symbols, hashes, arrays, and booleans.

22. What is the use of load and require in Ruby?

Ruby load and require both are used for loading code from libraries into the Ruby environment.

The difference between load and require is that with load, you’ll get a warning if the library has already been loaded in this process. With require, it will just throw an exception. The order of loading matters; for example:

require “lib” #=> NoMethodError::undefined method `has_key?’ for nil:NilClass (No match found)

load “lib” #LOAD OK true

puts lib[“key”] #=> nil (instance variable not set)

Explain Ruby if-else statement.

Ruby if-else state is used to test condition and then execute a statement if condition is true.

if n > 0

puts “positive”


puts “negative” #=> negative


23. What are the three Ruby built-in data structures? What’s their use case?

There are three built-in data structures in Ruby – arrays, hashes and sets. Arrays store items as indexed sequential lists while hashes provide mapping from keys to values. Sets are collections of unique elements where duplicate entries are not allowed

24. What are some differences between HTML/CSS and ERB?

This question will help you see their familiarity with existing languages that have similar syntaxes or structures as Ruby.

25. Explain for loop in Ruby.

A for loop is used to iterate over a range of numbers in Ruby. The syntax takes the form:

for n in 0..100 #=> iterates from 0 up to 100

26. What’s an Array? What are some common operations with it?

An array is simply a list of items and there are many different ways you can interact with them, including adding or removing elements at specific positions (e.g., delete item by position), modifying existing properties, searching through arrays via indices (position), or values (the contents themselves).

27. Explain Iteration vs Looping in Ruby

The difference between iteration and loops may not be clear if you don’t have programming experience but they both do similar things – each involves executing statements or commands over and over until a certain result is reached.

– Iteration refers to the process of traversing every member in an array, for example:

[“one”,”two”] -> [“one”, “two”]. As you traverse each element in the list, you can run any code inside your iteration statement.

– Looping on the other hand refers to executing statements or commands repeatedly within a particular context until some condition is met (or not). For instance:

(0…100).to_a[x] -> executes from 0 up to 100; it’s also known as enumeration because we’re counting something rather than iterating through elements like with arrays. The difference between this and regular loops is that you are bound to a certain range and you don’t have the power of iterating over all members.

28. Explain break statement in Ruby

It is a keyword that halts the execution of code in a given loop. It is mostly used in while loop for the case where we want to break from it.

29. Explain next statement in Ruby

It is the keyword to go one step ahead in a given loop. It’s mostly used in while loops for the case where we want to skip from it

30. Explain continue statement in Ruby

It tells Ruby that you don’t want to halt execution of code, just re-execute what follows next time around. It can be useful if you’re going through some sort of list and need the next item without having to wait until completion of previous actions; think ‘continue with current line’ or ‘next page’.

How will you comment in Ruby?

It can be accomplished with the following two ways.

– “#” to start a comment before line of code or

– “–>” for comments in between lines of code, and ending it by adding an end at the same level as where you want your comment to appear on.

31. What is block statement? What are its features?

Block statements allow us to group together any number of Ruby expressions that have local visibility within them, except those introduced by let or subject. They behave like blocks do in other languages such as Java or C++: they control their own lexical scope but also introduce new variables into the surrounding bulk (or current) context; these variables become part of what is called “the stack frame called the lexical closure.

32. Explain Ruby object

Normally, the Object class is considered to be the root of all Ruby objects. However, it functions in a supporting capacity for basic operations and then delegates other duties to more specialized classes.

33. Explain Proc in Ruby?

A Proc object is a type of function that wraps around any Ruby expression.

34. Explain what the “def” keyword does in ruby?

The def keyword defines a new method for an Object or Class; it will cause one to be created if it doesn’t already exist, and then turns its body into executable code.

35. What does self mean?

self always refers to the current object.

36. What are Ruby’s primitive data types?

The only primitives in Ruby are true and false. All other values—and everything else can be considered a “object” or some variation of the following:

  • nil, used to represent nothingness
  • symbols, like words that have meaning for humans but not computers (e.g., “yesterday”)
  • strings, which contain text from one character up to 60 characters long

We hope you find these Ruby interview questions helpful in sourcing the best candidate for your team! We may not have covered every single interview question, do your research to make sure you’re asking the right question during an interview process.

As always, please connect, and let’s talk about your Ruby on Rails needs!


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