Ruby

Question 1

What is a class in Ruby?

Answer 1

A class is a blueprint for creating objects. It defines the data and behaviors (methods) that its objects will have.

Question 2

How do you define a class in Ruby?

Answer 2

Use the ‘class’ keyword followed by the class name (CamelCase)

Question 3

What is an object in Ruby?

Answer 3

An object is an instance of a class. Almost everything in Ruby is an object

Question 4

How do you create an object from a class?

Answer 4

Call .new on the class: dog = Dog.new

Question 5

What is the initialize method used for?

Answer 5

It’s a constructor method that runs automatically when you create a new object. It usually sets up instance variables.

Question 6

How do you define an instance variable?

Answer 6

Start with ‘@’ inside a class. Example: @name = "Nick"

Question 7

What is the difference between an instance variable and a class variable?

Answer 7

An instance variable (@var) belongs to one object. A class variable (@@var) is shared among all instances of a class.

Question 8

What is a module in Ruby?

Answer 8

A module is a collection of methods and constants. It cannot be instantiated but can be included or extended into classes.

Question 9

How do you include a module into a class?

Answer 9

Use include ModuleName to add module methods as instance methods.

Question 10

How do you extend a module into a class?

Answer 10

Use extend ModuleName to add module methods as class methods.

Question 11

What is ‘Enumerable’ in Ruby?

Answer 11

A module that adds powerful iteration methods like map

Question 12

Which Ruby class includes the Enumerable module by default?

Answer 12

The Array and Hash classes (and any class that defines an each method).

Question 13

What does the ‘map’ method do?

Answer 13

It transforms each element in a collection based on a block and returns a new array of results.

Question 14

What does the ‘select’ method do?

Answer 14

It filters elements from a collection based on a condition in the block and returns those that evaluate to true.

Question 15

What does the ‘reduce’ (or ‘inject’) method do?

Answer 15

It accumulates a result across elements in a collection

Question 16

What is the difference between ‘each’ and ‘map’?

Answer 16

each iterates and returns the original array; map returns a new array with transformed elements.

Question 17

What is a block in Ruby?

Answer 17

A block is a chunk of code enclosed in {} or do...end that can be passed to methods for execution.

Question 18

How do you yield to a block inside a method?

Answer 18

Use the yield keyword to call the block passed to a method.

Question 19

What happens if you call yield without a block being given?

Answer 19

It raises a LocalJumpError unless you check with block_given? first.

Question 20

What are Procs in Ruby?

Answer 20

A Proc (procedure) is an object that encapsulates a block of code

Question 21

How do you create a Proc?

Answer 21

Use Proc.new { ... } or proc { ... }.

Question 22

How do you call a Proc?

Answer 22

Use .call on it

Question 23

What is a lambda in Ruby?

Answer 23

A lambda is similar to a Proc but checks arguments strictly and returns control differently.

Question 24

How do you create a lambda?

Answer 24

Use lambda { ... } or the shorthand -> { ... }.

Question 25

What is the difference between a Proc and a lambda?

Answer 25

Lambdas check the number of arguments and return to the calling method; Procs don’t check and return from the current scope.

Question 26

How can you pass a block as an argument to another method?

Answer 26

Prefix it with `&` when passing or receiving. Example: `def call_block(&block); block.call; end`

Question 27

How do you make your own class enumerable?

Answer 27

Include the Enumerable module and define an `each` method that yields items.

Question 28

What does 'self' refer to in Ruby?

Answer 28

It refers to the current object instance or the class itself when inside class-level context.

Question 29

What is method chaining?

Answer 29

It’s when you call multiple methods in a single expression

Question 30

How do you define a class method?

Answer 30

Prefix the method name with `self.` inside the class: `def self.say_hi; puts "Hi!"; end`

Question 31

What does attr_accessor do?

Answer 31

It automatically creates both getter and setter methods for an instance variable.