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31+ Ruby Interview Questions And Answers

Ruby is a dynamic, open-source programming language with a focus on simplicity and productivity. It has an elegant syntax that is natural to read and easy to write. Ruby is widely used for web development, notably as the language behind the popular Ruby on Rails web framework, as well as for scripting and data processing tasks. A sound knowledge of Ruby can open doors to various development projects and job opportunities. The following are Ruby interview questions designed to test the understanding of developers at both beginner and advanced levels.


Most asked Ruby interview questions



What is Ruby, and why is it popular among developers?

Ruby is a dynamic, object-oriented programming language known for its simplicity and productive features. It is popular among developers because of its elegant syntax, powerful framework capabilities, particularly Ruby on Rails, and its vibrant community.


How do you create a class in Ruby?

In Ruby, you can create a class by using the class keyword followed by the class name and the end keyword to close the class definition.

class Example


What is an instance variable?

An instance variable is a variable that is associated with a particular instance of a class. In Ruby, instance variables are prefixed with an '@' symbol.


Explain the concept of a symbol in Ruby.

A symbol in Ruby is a lightweight identifier often used as a label or key in hashes. It is immutable and represented with a colon followed by a name, such as :username.


Can you show how to define a method in Ruby that takes parameters?

def greet(name)
  # Method code goes here

Sure, you define a method in Ruby by using the def keyword, followed by the method name and parameters. Here is an example that greets a user by name:

def greet(name)
  puts "Hello \\(name)!"


What are blocks and how are they used in Ruby?

Blocks are anonymous pieces of code that can accept parameters and are enclosed by either braces {} or the do/end structure. They are often passed to methods as arguments and can be associated with yield statements within those methods.


What is the 'yield' keyword used for in Ruby?

The yield keyword is used inside a method to suspend its execution and transfer control to the block that was passed to the method. After the block execution, control is then handed back to the method.


Explain the difference between a local variable and a global variable.

A local variable is only accessible within the scope it is defined, such as within a method, whereas a global variable, which starts with a $ symbol, can be accessed from any part of the Ruby program.


How do you concatenate strings in Ruby?

In Ruby, you can concatenate strings using the + operator or the \ string interpolation method within double quotes.


What does the 'nil' value represent in Ruby?

In Ruby, nil represents nothing or an absence of value, akin to null in other programming languages. It also serves as the return value for methods that do not explicitly return anything.


How can you convert a string to an integer?

To convert a string to an integer in Ruby, you can use the to_i method on the string.


Describe how to use array methods such as 'map' and 'select'.

The map method in Ruby is used to transform the elements of an array, returning a new array with the results. The select method is used to filter an array based on a condition, returning a new array containing elements that match the condition.


Explain the '==' and '===' operators.

The == operator in Ruby is used for checking equality between two objects, while the === (case equality) operator is more versatile and used in case statements to test a value against a range, class, or regular expression.


What is a Range, and how do you create one?

A Range represents a sequence of numbers or letters. In Ruby, you create a Range using two numbers or letters with two or three dots between them, like 1..10 or 'a'...'z'.


What will the following code output?

puts 'Ruby' == 'Ruby'
puts :ruby == :ruby

The code will output true twice as both string and symbol comparisons return true since their values match.

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Describe metaprogramming and its use in Ruby.

Metaprogramming refers to writing code that generates other code during runtime. In Ruby, it's used for creating methods dynamically, altering class inheritance, and more. This powerful feature leverages Ruby's reflective abilities.


What are some ways to call a method dynamically?

You can call a method dynamically using the send method or with method(:method_name).call. Both allow you to invoke a method when you don't know which method will be called ahead of time.


How do you handle exceptions in Ruby?

You handle exceptions in Ruby using a begin/rescue/end block. The code that could raise an exception is placed in the begin block, and the rescue block contains code to run if an exception occurs.


Can you explain the difference between 'include' and 'extend' when using modules?

include makes a module's methods available as instance methods of the class, while extend makes them available as class methods.


How do you declare and use a constant in Ruby?

You declare a constant in Ruby by starting its name with an uppercase letter. Constants are intended to remain unchanged once assigned.


What is a proc, and how does it differ from a lambda?

A proc is a type of closure in Ruby, similar to a block but can be stored in a variable. Lambdas are a type of proc with stricter argument handling and distinct return behavior—they return from the lambda itself rather than the encompassing method.


Discuss the garbage collection system in Ruby.

Ruby uses a mark-and-sweep garbage collection algorithm. It marks objects that are still in use and sweeps away those that aren't to free up memory.


What will this code return and why?

def check_binding
  value = 123

context = check_binding

The code will return 123. The 'binding' method captures the context of the method's local and instance variables at the point of method execution, allowing 'context.eval' to access 'value'.


How do you create a mixin, and why would you use it?

You create a mixin in Ruby by declaring a module and including it in a class using the include keyword. Mixins allow for code reusability and adding functions to a class without traditional inheritance.


Explain how you can serialize and deserialize objects in Ruby.

You can use methods like Marshal.dump to serialize an object to a byte stream and Marshal.load to deserialize it back into a Ruby object.


Discuss the role of the load path ($LOAD_PATH / $:) in Ruby.

The load path is a collection of directory paths that Ruby searches when looking to load files with require or load. Adding directories to this path allows Ruby to find and include external libraries.


Show how you could refactor the following code to make it more Ruby idiomatic. { |item| item * item }

To make this code more Ruby idiomatic, you can use the collect method with a shorthand block, like so:



Explain the concept of Duck Typing in Ruby.

Duck Typing is a programming concept in Ruby where the class of an object is less important than the methods it defines. As the saying goes, 'If it quacks like a duck, it is a duck.' It allows for flexible method invocation.


What is the purpose of the self keyword, and where can it be used?

In Ruby, self refers to the current object, context, or class. It is used within methods to refer to the object instance or within class and module definitions to refer to the class or module itself.


How do you test if a variable is an instance of a particular class or module?

You can test if a variable is an instance of a class or module using the is_a? or kind_of? methods.


Write a code sample that demonstrates the use of a module as a namespace.

Sure, here's how you can define a module as a namespace for a class:

module MyNamespace
  class MyClass
    # Class implementation

instance =

Ruby Interview Tips

Understanding the Question

  • When facing a challenging interview question, first and foremost, ensure you fully understand the question. Ask for clarification if necessary, rather than making assumptions about what is being asked. Use active listening techniques, and when the interviewer finishes, repeat the question back in your own words to confirm your understanding. This shows the interviewer that you are thorough and attentive, which are desirable traits in a candidate. Additionally, this step ensures that you don’t waste time answering the wrong question.

Take Time to Think

  • It’s perfectly acceptable to take a moment to think before you answer a difficult question. Inform the interviewer that you need a bit of time to collect your thoughts. This period allows you to organize your answer and calm your nerves, leading to a more composed and articulate response. In this quiet time, try to break the question into smaller parts that you can tackle one by one, and recall any relevant knowledge or experience you have that could be used to construct your answer.

Structure Your Response

  • When you begin to answer, structure your thoughts clearly. A common technique for tough problem-solving questions is to use the STAR method (Situation, Task, Action, Result) which is particularly helpful in behavioral interviews. Even technical questions can be approached in a structured way by explaining your thought process, the potential solutions you considered, the choice you've made, and the reason behind it. This structured response not only helps the interviewer follow your answer but also demonstrates your systematic approach to problem-solving.

Be Honest About Your Expertise

  • If a tough question arises and it lies outside your area of expertise, be honest with the interviewer about it. Transparency about your skills and knowledge can be a testament to your integrity. However, don't just stop at admitting your unfamiliarity; express your eagerness to learn and how you approach new challenges. You might also try to relate the question to something you are familiar with, showing your ability to connect the dots and apply your knowledge to different contexts.

Keep Calm and Carry On

  • Tough questions can easily throw you off your game if you allow them to disrupt your confidence. Remember to keep calm and maintain a positive demeanor, even if the question seems daunting or if you don't know the answer immediately. Your attitude in the face of adversity can be just as telling as the answer itself. Displaying composure under pressure is an invaluable skill in many job roles, and interviews are a prime opportunity to showcase this trait.


How much do Ruby developers make?

Salaries for Ruby developers vary widely depending on experience and location, but they generally command competitive rates in the tech industry. Read more: How much do Ruby developers make?

Are Ruby devs in demand?

Yes, Ruby developers remain in demand due to the enduring popularity of Ruby on Rails and the need for skilled back-end developers. Read more: Are Ruby devs in demand?

How much does it cost to develop Ruby on Rails?

The cost of developing a Ruby on Rails project can vary based on complexity, but it tends to be cost-effective due to rapid development capabilities. Read more: How much does it cost to develop Ruby on Rails?

Why using FireHire for hiring Ruby developers is the best choice?

FireHire offers a unique blend of pre-vetted senior devs, risk-free hiring with a replacement guarantee, and an extensive talent pool, ensuring you find the ideal Ruby expert efficiently.

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