Ruby interview questions

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Ruby interview questions

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Question

Does Ruby support namespaces?

Answer

A namespace provides a container to hold things like functions, classes and constants as a way to group them together logically and to help avoid conflicts with functions and classes with the same name that have been written by someone else.

In Ruby this is achieved using modules.

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Question

How can I invoke a method in Ruby?

Answer

There are three ways to invoke a method in Ruby - dot operator (or period operator), the Object#send method or method(:foo).call:

object = Object.new
puts object.object_id

puts object.send(:object_id)

puts object.method(:object_id).call

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Question

What does self mean in Ruby?

Answer

It is receiver object of the current method. In Ruby language for method invocation it's prefered to say "message passing". So in other words, self is the object to which the message (or method) has been sent. For example, in the following code reflect is an instance method. It belongs to the object we created via Ghost.new. So self points to that object.

class Ghost
  def reflect
    self
  end
end

g = Ghost.new
g.reflect == g # => true

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Question

Explain how you define an Instance Variable, Global Variable and Class Variable in Ruby?

Answer

Ruby Instance variable begins with — @
Ruby Class variables begin with — @@
Ruby Global variables begin with — $

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Question

Explain how can you declare a block in Ruby?

Answer

In Ruby, the code in the block is always enclosed within braces ({}). You can invoke a block by using “yield statement”.

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Question

What is Interpolation in Ruby?

Answer

Ruby Interpolation is the process of inserting a string into a literal. By placing a Hash (#) within {} open and close brackets, one can interpolate a string into the literal. For example:

name = "Alex"
puts "Hello, #{name}!"

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Question

What is a lambda?

Answer

In Ruby a lambda is just an anonymous function. Lambdas in Ruby are also objects, just like everything else. Lambda can return a value. Example:

l = lambda do |name|
  return "Hello, #{name}!"
end
puts l.call("Alex")

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Question

What are levels of method access control for classes in Ruby?

Answer

There are three levels of method access control for classes:

Public methods - can be called by all objects and subclasses of the class in which they are defined in.
Protected methods - only accessible to objects within the same class.
Private methods - are only accessible within the same instance.

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Question

How would you create getter and setter methods in Ruby?

Answer

Of course you can create them manually. But the more elegant way is to call the attr_accessor method which generates it's for you.

class Person
  attr_accessor :name
end

You can also generate just getter or setter individuall using attr_reader and attr_writer moethods appropriately.

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Question

How does a symbol differ from a string?

Answer

The main difference is that multiple symbols representing a single value are identical whereas this is not true with strings. It is also faster to compare symbols for equality since they are the same object.

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