Ruby Programming Practice Exam

Question 1 Ruby Programming

What are attr_accessor, attr_reader, and attr_writer?

each is the most common iterator. It passes each element of a collection to a block.
Example:
[10, 20, 30].each { |n| puts n }
It returns the original collection. yield transfers control from a method to the block passed to it.
Example:

def greet
  yield("World") if block_given?
end
greet { |name| puts "Hello, #{name}!" }

These are class macros that generate getter/setter methods:

attr_reader :name — getter only
attr_writer :name — setter only
attr_accessor :name — both getter and setter

They replace manually defining def name and def name=. Class variables start with @@ and are shared among all instances of a class and its subclasses.
Example:
@@count = 0
Use with caution as subclasses share the same variable.

Question 2 Ruby Programming

What are class variables in Ruby?

OpenStruct (from the ostruct library) creates objects with arbitrary attributes defined at runtime.
Example:

require "ostruct"
person = OpenStruct.new(name: "Alice", age: 30)
person.name # => "Alice"

Class variables start with @@ and are shared among all instances of a class and its subclasses.
Example:
@@count = 0
Use with caution as subclasses share the same variable. Instance variables start with @ and belong to a specific object instance. They persist for the lifetime of the object.
Example: @name = "Ruby" Metaprogramming is writing code that writes or modifies code at runtime. Ruby supports it extensively with methods like define_method, method_missing, and send.
It allows dynamic creation of methods, classes, and modules.

Question 3 Ruby Programming

What is a Module in Ruby?

yield transfers control from a method to the block passed to it.
Example:

def greet
  yield("World") if block_given?
end
greet { |name| puts "Hello, #{name}!" }

A Lambda is a special type of Proc that enforces the correct number of arguments and returns control to the calling method.
Example:
square = ->(x) { x * x }
square.call(5) # => 25 A Module is a container for methods and constants that cannot be instantiated. Modules serve two purposes:

Namespacing: grouping related classes/methods.
Mixins: sharing behavior across classes via include or extend.

Metaprogramming is writing code that writes or modifies code at runtime. Ruby supports it extensively with methods like define_method, method_missing, and send.
It allows dynamic creation of methods, classes, and modules.

Question 4 Ruby Programming

What is the splat operator (*) in Ruby?

The splat operator * collects or expands arguments:

Collect: def foo(*args) gathers extra arguments into an array.
Expand: method(*array) passes array elements as separate arguments.

Double splat ** works the same way for keyword arguments. The & operator converts between blocks and Procs:

&block in a parameter captures a block as a Proc.
&proc in a method call converts a Proc into a block.

Example:

def run(&blk)
  blk.call
end

block_given? returns true if a block was passed to the current method, false otherwise. It prevents a LocalJumpError when calling yield without a block.
Example:

def safe_call
  yield if block_given?
end

yield transfers control from a method to the block passed to it.
Example:

def greet
  yield("World") if block_given?
end
greet { |name| puts "Hello, #{name}!" }

Question 5 Ruby Programming

What are instance variables in Ruby?

A Range represents an interval of values using .. (inclusive) or ... (exclusive).
Examples:
(1..5).to_a # => [1, 2, 3, 4, 5]
(1...5).to_a # => [1, 2, 3, 4]
Ranges work with numbers, strings, and any object implementing <=>. The splat operator * collects or expands arguments:

Collect: def foo(*args) gathers extra arguments into an array.
Expand: method(*array) passes array elements as separate arguments.

Double splat ** works the same way for keyword arguments. A Hash is a collection of key-value pairs.
Examples:
h = { name: "Alice", age: 30 }
h = Hash.new(0)
Access values with h[:name]. Instance variables start with @ and belong to a specific object instance. They persist for the lifetime of the object.
Example: @name = "Ruby"

Question 6 Ruby Programming

What is the initialize method in a Ruby class?

Use File.read or File.open with a block:
content = File.read("file.txt")
Or line by line:
File.foreach("file.txt") { |line| puts line }
Using a block with File.open automatically closes the file. Use the class keyword:

class Dog
  def initialize(name)
    @name = name
  end
  def bark
    "Woof!"
  end
end

initialize is the constructor method called automatically when you create a new object with ClassName.new. It is used to set up instance variables.
Example:

def initialize(name)
  @name = name
end

The ensure block runs regardless of whether an exception was raised or not. It is used for cleanup tasks like closing files or releasing resources.
Example:

begin
  file = File.open("data.txt")
rescue
  puts "Error"
ensure
  file&.close
end

Question 7 Ruby Programming

What is the safe navigation operator (&.) in Ruby?

The safe navigation operator &. calls a method only if the receiver is not nil, returning nil otherwise.
Example:
user&.name
This avoids NoMethodError on nil objects. Equivalent to user && user.name. A Mixin is a module included in a class to add shared behavior, providing a form of multiple inheritance.
Example:

module Greetable
  def greet
    "Hello!"
  end
end
class User
  include Greetable
end

Metaprogramming is writing code that writes or modifies code at runtime. Ruby supports it extensively with methods like define_method, method_missing, and send.
It allows dynamic creation of methods, classes, and modules. include adds module methods as instance methods of the class.
extend adds module methods as class methods.
Example:

class Foo
  include MyModule  # instance methods
  extend MyModule   # class methods
end

Question 8 Ruby Programming

What are regular expressions in Ruby?

reduce (alias inject) combines all elements by applying a binary operation, accumulating a single result.
Example:

[1,2,3,4].reduce(0) { |sum, n| sum + n }
# => 10

send invokes a method by name (as a symbol or string), including private methods.
Example:
obj.send(:my_method, arg1)
Use public_send to restrict to public methods only for safety.

== — checks value equality (can be overridden).
eql? — checks value and type equality (used by Hash for keys).
equal? — checks object identity (same object_id).

Example: 1 == 1.0 # true, 1.eql?(1.0) # false Regular expressions (regex) are patterns enclosed in forward slashes used for matching strings.
Example:

/\d+/.match("abc123")
# => #<MatchData "123">

Use =~ operator: "hello" =~ /ell/ # => 1

Question 9 Ruby Programming

What is inheritance in Ruby?

select returns a new array containing elements for which the block returns true.
Example:

[1,2,3,4,5].select { |n| n.even? }
# => [2, 4]

Key differences:

Argument checking: Lambdas raise an error on wrong argument count; Procs assign nil to missing args.
Return behavior: return in a Lambda exits the lambda; return in a Proc exits the enclosing method.

map (alias collect) returns a new array with the results of running the block for every element.
Example:

[1,2,3].map { |n| n * 2 }
# => [2, 4, 6]

Inheritance lets a class derive behavior from a parent class using <.
Example:

class Dog < Animal
  def speak
    "Woof"
  end
end

Ruby supports single inheritance only.

Question 10 Ruby Programming

How do you use gsub with a regex in Ruby?

The safe navigation operator &. calls a method only if the receiver is not nil, returning nil otherwise.
Example:
user&.name
This avoids NoMethodError on nil objects. Equivalent to user && user.name. Use File.open with the "w" mode:

File.open("out.txt", "w") do |f|
  f.puts "Hello, world!"
end

Use "a" mode to append instead of overwriting. include adds module methods as instance methods of the class.
extend adds module methods as class methods.
Example:

class Foo
  include MyModule  # instance methods
  extend MyModule   # class methods
end

gsub replaces all occurrences matching a pattern:

"hello world".gsub(/[aeiou]/, "*")
# => "h*ll* w*rld"

You can also pass a block:
"cat bat".gsub(/\b\w/) { |m| m.upcase }

Question 11 Ruby Programming

How do you define a class in Ruby?

Use the class keyword:

class Dog
  def initialize(name)
    @name = name
  end
  def bark
    "Woof!"
  end
end

The ternary operator is a concise conditional expression:
condition ? true_value : false_value
Example:
status = age >= 18 ? "adult" : "minor" block_given? returns true if a block was passed to the current method, false otherwise. It prevents a LocalJumpError when calling yield without a block.
Example:

def safe_call
  yield if block_given?
end

Class variables start with @@ and are shared among all instances of a class and its subclasses.
Example:
@@count = 0
Use with caution as subclasses share the same variable.

Question 12 Ruby Programming

What is a Gem in Ruby?

include adds module methods as instance methods of the class.
extend adds module methods as class methods.
Example:

class Foo
  include MyModule  # instance methods
  extend MyModule   # class methods
end

A Module is a container for methods and constants that cannot be instantiated. Modules serve two purposes:

Namespacing: grouping related classes/methods.
Mixins: sharing behavior across classes via include or extend.

A Gem is a packaged Ruby library or application distributed via RubyGems.
Install with: gem install rails
Manage project dependencies with a Gemfile and Bundler:
bundle install The safe navigation operator &. calls a method only if the receiver is not nil, returning nil otherwise.
Example:
user&.name
This avoids NoMethodError on nil objects. Equivalent to user && user.name.

Question 13 Ruby Programming

What does the reduce method do in Ruby?

A Gem is a packaged Ruby library or application distributed via RubyGems.
Install with: gem install rails
Manage project dependencies with a Gemfile and Bundler:
bundle install A Mixin is a module included in a class to add shared behavior, providing a form of multiple inheritance.
Example:

module Greetable
  def greet
    "Hello!"
  end
end
class User
  include Greetable
end

reduce (alias inject) combines all elements by applying a binary operation, accumulating a single result.
Example:

[1,2,3,4].reduce(0) { |sum, n| sum + n }
# => 10

Use File.read or File.open with a block:
content = File.read("file.txt")
Or line by line:
File.foreach("file.txt") { |line| puts line }
Using a block with File.open automatically closes the file.

Question 14 Ruby Programming

What does send do in Ruby?

send invokes a method by name (as a symbol or string), including private methods.
Example:
obj.send(:my_method, arg1)
Use public_send to restrict to public methods only for safety. These are class macros that generate getter/setter methods:

attr_reader :name — getter only
attr_writer :name — setter only
attr_accessor :name — both getter and setter

They replace manually defining def name and def name=. Metaprogramming is writing code that writes or modifies code at runtime. Ruby supports it extensively with methods like define_method, method_missing, and send.
It allows dynamic creation of methods, classes, and modules. The Comparable module provides comparison operators (<, <=, ==, >=, >) when you define the <=> (spaceship) method.
Example:

class Box
  include Comparable
  def <=>(other)
    self.size <=> other.size
  end
end

Question 15 Ruby Programming

What is the Enumerable module in Ruby?

map (alias collect) returns a new array with the results of running the block for every element.
Example:

[1,2,3].map { |n| n * 2 }
# => [2, 4, 6]

Enumerable provides collection methods like map, select, reduce, sort, and min. Include it in your class and define an each method to gain all these methods automatically. A Module is a container for methods and constants that cannot be instantiated. Modules serve two purposes:

Namespacing: grouping related classes/methods.
Mixins: sharing behavior across classes via include or extend.

Bundler manages gem dependencies for a Ruby project. It reads the Gemfile, resolves versions, and generates a Gemfile.lock.
Commands:

bundle install — install dependencies
bundle exec — run commands in the bundle context

Question 16 Ruby Programming

What are the differences between a Proc and a Lambda?

puts — prints with a newline, calls .to_s.
print — prints without a newline, calls .to_s.
p — prints the .inspect output with a newline (useful for debugging).

Example: p [1,2] outputs [1, 2]. Key differences:

Argument checking: Lambdas raise an error on wrong argument count; Procs assign nil to missing args.
Return behavior: return in a Lambda exits the lambda; return in a Proc exits the enclosing method.

method_missing is called when an object receives a message it cannot handle. You can override it to intercept undefined method calls.
Example:

def method_missing(name, *args)
  puts "Called: #{name}"
end

Always define respond_to_missing? alongside it. These are class macros that generate getter/setter methods:

attr_reader :name — getter only
attr_writer :name — setter only
attr_accessor :name — both getter and setter

They replace manually defining def name and def name=.

Question 17 Ruby Programming

What does method_missing do in Ruby?

initialize is the constructor method called automatically when you create a new object with ClassName.new. It is used to set up instance variables.
Example:

def initialize(name)
  @name = name
end

The & operator converts between blocks and Procs:

&block in a parameter captures a block as a Proc.
&proc in a method call converts a Proc into a block.

Example:

def run(&blk)
  blk.call
end

A Gem is a packaged Ruby library or application distributed via RubyGems.
Install with: gem install rails
Manage project dependencies with a Gemfile and Bundler:
bundle install method_missing is called when an object receives a message it cannot handle. You can override it to intercept undefined method calls.
Example:

def method_missing(name, *args)
  puts "Called: #{name}"
end

Always define respond_to_missing? alongside it.

Question 18 Ruby Programming

What is the difference between puts, print, and p in Ruby?

Instance variables start with @ and belong to a specific object instance. They persist for the lifetime of the object.
Example: @name = "Ruby" Use File.open with the "w" mode:

File.open("out.txt", "w") do |f|
  f.puts "Hello, world!"
end

Use "a" mode to append instead of overwriting.

puts — prints with a newline, calls .to_s.
print — prints without a newline, calls .to_s.
p — prints the .inspect output with a newline (useful for debugging).

Example: p [1,2] outputs [1, 2]. OpenStruct (from the ostruct library) creates objects with arbitrary attributes defined at runtime.
Example:

require "ostruct"
person = OpenStruct.new(name: "Alice", age: 30)
person.name # => "Alice"

Question 19 Ruby Programming

How do you create an Array in Ruby?

An Array is an ordered collection created with square brackets or Array.new.
Examples:
nums = [1, 2, 3]
words = %w[hello world]
empty = Array.new(5, 0) A Proc is an object that encapsulates a block of code, allowing it to be stored in a variable and called later.
Example:
greet = Proc.new { |name| puts "Hello, #{name}" }
greet.call("Alice") The & operator converts between blocks and Procs:

&block in a parameter captures a block as a Proc.
&proc in a method call converts a Proc into a block.

Example:

def run(&blk)
  blk.call
end

A block is an anonymous chunk of code enclosed in do...end or curly braces { } that can be passed to a method.
Example:
[1,2,3].each { |n| puts n }

Question 20 Ruby Programming

What does the select method do in Ruby?

An Array is an ordered collection created with square brackets or Array.new.
Examples:
nums = [1, 2, 3]
words = %w[hello world]
empty = Array.new(5, 0) A Module is a container for methods and constants that cannot be instantiated. Modules serve two purposes:

Namespacing: grouping related classes/methods.
Mixins: sharing behavior across classes via include or extend.

A Proc is an object that encapsulates a block of code, allowing it to be stored in a variable and called later.
Example:
greet = Proc.new { |name| puts "Hello, #{name}" }
greet.call("Alice") select returns a new array containing elements for which the block returns true.
Example:

[1,2,3,4,5].select { |n| n.even? }
# => [2, 4]

Question 21 Ruby Programming

How do you handle exceptions in Ruby?

reduce (alias inject) combines all elements by applying a binary operation, accumulating a single result.
Example:

[1,2,3,4].reduce(0) { |sum, n| sum + n }
# => 10

A Module is a container for methods and constants that cannot be instantiated. Modules serve two purposes:

Namespacing: grouping related classes/methods.
Mixins: sharing behavior across classes via include or extend.

Use begin...rescue...end:

begin
  risky_operation
rescue StandardError => e
  puts e.message
ensure
  cleanup
end

The ensure block always executes. Both define blocks, but curly braces { } have higher precedence than do...end.
Convention: use { } for single-line blocks and do...end for multi-line blocks.

Question 22 Ruby Programming

What is open_struct in Ruby?

Create a class inheriting from StandardError:

class MyError < StandardError; end
raise MyError, "Something went wrong"

Catch it with rescue MyError => e. A Gem is a packaged Ruby library or application distributed via RubyGems.
Install with: gem install rails
Manage project dependencies with a Gemfile and Bundler:
bundle install A Lambda is a special type of Proc that enforces the correct number of arguments and returns control to the calling method.
Example:
square = ->(x) { x * x }
square.call(5) # => 25 OpenStruct (from the ostruct library) creates objects with arbitrary attributes defined at runtime.
Example:

require "ostruct"
person = OpenStruct.new(name: "Alice", age: 30)
person.name # => "Alice"

Question 23 Ruby Programming

What is the each iterator in Ruby?

The safe navigation operator &. calls a method only if the receiver is not nil, returning nil otherwise.
Example:
user&.name
This avoids NoMethodError on nil objects. Equivalent to user && user.name. each is the most common iterator. It passes each element of a collection to a block.
Example:
[10, 20, 30].each { |n| puts n }
It returns the original collection. The & operator converts between blocks and Procs:

&block in a parameter captures a block as a Proc.
&proc in a method call converts a Proc into a block.

Example:

def run(&blk)
  blk.call
end

A Mixin is a module included in a class to add shared behavior, providing a form of multiple inheritance.
Example:

module Greetable
  def greet
    "Hello!"
  end
end
class User
  include Greetable
end

Question 24 Ruby Programming

What is a Lambda in Ruby?

gsub replaces all occurrences matching a pattern:

"hello world".gsub(/[aeiou]/, "*")
# => "h*ll* w*rld"

You can also pass a block:
"cat bat".gsub(/\b\w/) { |m| m.upcase } A Lambda is a special type of Proc that enforces the correct number of arguments and returns control to the calling method.
Example:
square = ->(x) { x * x }
square.call(5) # => 25 yield transfers control from a method to the block passed to it.
Example:

def greet
  yield("World") if block_given?
end
greet { |name| puts "Hello, #{name}!" }

select returns a new array containing elements for which the block returns true.
Example:

[1,2,3,4,5].select { |n| n.even? }
# => [2, 4]

Question 25 Ruby Programming

How do you use the case/when statement in Ruby?

initialize is the constructor method called automatically when you create a new object with ClassName.new. It is used to set up instance variables.
Example:

def initialize(name)
  @name = name
end

Use File.open with the "w" mode:

File.open("out.txt", "w") do |f|
  f.puts "Hello, world!"
end

Use "a" mode to append instead of overwriting. case provides pattern-matching control flow:

case grade
when "A" then "Excellent"
when "B" then "Good"
when "C" then "Average"
else "Needs improvement"
end

It uses the === operator, so it works with ranges, classes, and regex too. An Array is an ordered collection created with square brackets or Array.new.
Examples:
nums = [1, 2, 3]
words = %w[hello world]
empty = Array.new(5, 0)

Question 26 Ruby Programming

What is a block in Ruby?

An Array is an ordered collection created with square brackets or Array.new.
Examples:
nums = [1, 2, 3]
words = %w[hello world]
empty = Array.new(5, 0) The & operator converts between blocks and Procs:

&block in a parameter captures a block as a Proc.
&proc in a method call converts a Proc into a block.

Example:

def run(&blk)
  blk.call
end

Regular expressions (regex) are patterns enclosed in forward slashes used for matching strings.
Example:

/\d+/.match("abc123")
# => #<MatchData "123">

Use =~ operator: "hello" =~ /ell/ # => 1 A block is an anonymous chunk of code enclosed in do...end or curly braces { } that can be passed to a method.
Example:
[1,2,3].each { |n| puts n }

Question 27 Ruby Programming

What does the map method do in Ruby?

map (alias collect) returns a new array with the results of running the block for every element.
Example:

[1,2,3].map { |n| n * 2 }
# => [2, 4, 6]

Class variables start with @@ and are shared among all instances of a class and its subclasses.
Example:
@@count = 0
Use with caution as subclasses share the same variable. These are class macros that generate getter/setter methods:

attr_reader :name — getter only
attr_writer :name — setter only
attr_accessor :name — both getter and setter

They replace manually defining def name and def name=. The & operator converts between blocks and Procs:

&block in a parameter captures a block as a Proc.
&proc in a method call converts a Proc into a block.

Example:

def run(&blk)
  blk.call
end

Question 28 Ruby Programming

How do you create a Hash in Ruby?

A Hash is a collection of key-value pairs.
Examples:
h = { name: "Alice", age: 30 }
h = Hash.new(0)
Access values with h[:name]. Enumerable provides collection methods like map, select, reduce, sort, and min. Include it in your class and define an each method to gain all these methods automatically. freeze makes an object immutable. Any attempt to modify a frozen object raises a FrozenError.
Example:

str = "hello"
str.freeze
str << " world" # => FrozenError

Check with str.frozen?. The safe navigation operator &. calls a method only if the receiver is not nil, returning nil otherwise.
Example:
user&.name
This avoids NoMethodError on nil objects. Equivalent to user && user.name.

Question 29 Ruby Programming

How do you create a Range in Ruby?

freeze makes an object immutable. Any attempt to modify a frozen object raises a FrozenError.
Example:

str = "hello"
str.freeze
str << " world" # => FrozenError

Check with str.frozen?. Instance variables start with @ and belong to a specific object instance. They persist for the lifetime of the object.
Example: @name = "Ruby" include adds module methods as instance methods of the class.
extend adds module methods as class methods.
Example:

class Foo
  include MyModule  # instance methods
  extend MyModule   # class methods
end

A Range represents an interval of values using .. (inclusive) or ... (exclusive).
Examples:
(1..5).to_a # => [1, 2, 3, 4, 5]
(1...5).to_a # => [1, 2, 3, 4]
Ranges work with numbers, strings, and any object implementing <=>.

Question 30 Ruby Programming

What is the Comparable module in Ruby?

include adds module methods as instance methods of the class.
extend adds module methods as class methods.
Example:

class Foo
  include MyModule  # instance methods
  extend MyModule   # class methods
end

Metaprogramming is writing code that writes or modifies code at runtime. Ruby supports it extensively with methods like define_method, method_missing, and send.
It allows dynamic creation of methods, classes, and modules. initialize is the constructor method called automatically when you create a new object with ClassName.new. It is used to set up instance variables.
Example:

def initialize(name)
  @name = name
end

The Comparable module provides comparison operators (<, <=, ==, >=, >) when you define the <=> (spaceship) method.
Example:

class Box
  include Comparable
  def <=>(other)
    self.size <=> other.size
  end
end

Question 31 Ruby Programming

What is the freeze method in Ruby?

The splat operator * collects or expands arguments:

Collect: def foo(*args) gathers extra arguments into an array.
Expand: method(*array) passes array elements as separate arguments.

Double splat ** works the same way for keyword arguments. Use File.open with the "w" mode:

File.open("out.txt", "w") do |f|
  f.puts "Hello, world!"
end

Use "a" mode to append instead of overwriting. freeze makes an object immutable. Any attempt to modify a frozen object raises a FrozenError.
Example:

str = "hello"
str.freeze
str << " world" # => FrozenError

Check with str.frozen?. Both define blocks, but curly braces { } have higher precedence than do...end.
Convention: use { } for single-line blocks and do...end for multi-line blocks.

Question 32 Ruby Programming

What is a Proc in Ruby?

OpenStruct (from the ostruct library) creates objects with arbitrary attributes defined at runtime.
Example:

require "ostruct"
person = OpenStruct.new(name: "Alice", age: 30)
person.name # => "Alice"

Bundler manages gem dependencies for a Ruby project. It reads the Gemfile, resolves versions, and generates a Gemfile.lock.
Commands:

bundle install — install dependencies
bundle exec — run commands in the bundle context

== — checks value equality (can be overridden).
eql? — checks value and type equality (used by Hash for keys).
equal? — checks object identity (same object_id).

Example: 1 == 1.0 # true, 1.eql?(1.0) # false A Proc is an object that encapsulates a block of code, allowing it to be stored in a variable and called later.
Example:
greet = Proc.new { |name| puts "Hello, #{name}" }
greet.call("Alice")

Question 33 Ruby Programming

How do you write to a file in Ruby?

The ensure block runs regardless of whether an exception was raised or not. It is used for cleanup tasks like closing files or releasing resources.
Example:

begin
  file = File.open("data.txt")
rescue
  puts "Error"
ensure
  file&.close
end

Use File.open with the "w" mode:

File.open("out.txt", "w") do |f|
  f.puts "Hello, world!"
end

Use "a" mode to append instead of overwriting. A Mixin is a module included in a class to add shared behavior, providing a form of multiple inheritance.
Example:

module Greetable
  def greet
    "Hello!"
  end
end
class User
  include Greetable
end

Class variables start with @@ and are shared among all instances of a class and its subclasses.
Example:
@@count = 0
Use with caution as subclasses share the same variable.

Question 34 Ruby Programming

What is the purpose of the ensure block in exception handling?

Use begin...rescue...end:

begin
  risky_operation
rescue StandardError => e
  puts e.message
ensure
  cleanup
end

The ensure block always executes. The ensure block runs regardless of whether an exception was raised or not. It is used for cleanup tasks like closing files or releasing resources.
Example:

begin
  file = File.open("data.txt")
rescue
  puts "Error"
ensure
  file&.close
end

Inheritance lets a class derive behavior from a parent class using <.
Example:

class Dog < Animal
  def speak
    "Woof"
  end
end

Ruby supports single inheritance only. initialize is the constructor method called automatically when you create a new object with ClassName.new. It is used to set up instance variables.
Example:

def initialize(name)
  @name = name
end

Question 35 Ruby Programming

What is the ternary operator in Ruby?

method_missing is called when an object receives a message it cannot handle. You can override it to intercept undefined method calls.
Example:

def method_missing(name, *args)
  puts "Called: #{name}"
end

Always define respond_to_missing? alongside it. The splat operator * collects or expands arguments:

Collect: def foo(*args) gathers extra arguments into an array.
Expand: method(*array) passes array elements as separate arguments.

Double splat ** works the same way for keyword arguments. The ternary operator is a concise conditional expression:
condition ? true_value : false_value
Example:
status = age >= 18 ? "adult" : "minor" block_given? returns true if a block was passed to the current method, false otherwise. It prevents a LocalJumpError when calling yield without a block.
Example:

def safe_call
  yield if block_given?
end

Question 36 Ruby Programming

How do you read a file in Ruby?

== — checks value equality (can be overridden).
eql? — checks value and type equality (used by Hash for keys).
equal? — checks object identity (same object_id).

Example: 1 == 1.0 # true, 1.eql?(1.0) # false Use File.read or File.open with a block:
content = File.read("file.txt")
Or line by line:
File.foreach("file.txt") { |line| puts line }
Using a block with File.open automatically closes the file. A Mixin is a module included in a class to add shared behavior, providing a form of multiple inheritance.
Example:

module Greetable
  def greet
    "Hello!"
  end
end
class User
  include Greetable
end

The Comparable module provides comparison operators (<, <=, ==, >=, >) when you define the <=> (spaceship) method.
Example:

class Box
  include Comparable
  def <=>(other)
    self.size <=> other.size
  end
end

Question 37 Ruby Programming

What is the difference between == and eql? and equal? in Ruby?

each is the most common iterator. It passes each element of a collection to a block.
Example:
[10, 20, 30].each { |n| puts n }
It returns the original collection. select returns a new array containing elements for which the block returns true.
Example:

[1,2,3,4,5].select { |n| n.even? }
# => [2, 4]

== — checks value equality (can be overridden).
eql? — checks value and type equality (used by Hash for keys).
equal? — checks object identity (same object_id).

Example: 1 == 1.0 # true, 1.eql?(1.0) # false reduce (alias inject) combines all elements by applying a binary operation, accumulating a single result.
Example:

[1,2,3,4].reduce(0) { |sum, n| sum + n }
# => 10

Question 38 Ruby Programming

What is the difference between include and extend in Ruby?

A Proc is an object that encapsulates a block of code, allowing it to be stored in a variable and called later.
Example:
greet = Proc.new { |name| puts "Hello, #{name}" }
greet.call("Alice") Use the class keyword:

class Dog
  def initialize(name)
    @name = name
  end
  def bark
    "Woof!"
  end
end

include adds module methods as instance methods of the class.
extend adds module methods as class methods.
Example:

class Foo
  include MyModule  # instance methods
  extend MyModule   # class methods
end

select returns a new array containing elements for which the block returns true.
Example:

[1,2,3,4,5].select { |n| n.even? }
# => [2, 4]

Question 39 Ruby Programming

What is a Symbol in Ruby?

map (alias collect) returns a new array with the results of running the block for every element.
Example:

[1,2,3].map { |n| n * 2 }
# => [2, 4, 6]

A Symbol is a lightweight, immutable identifier prefixed with a colon, e.g. :name. Symbols are stored in memory only once, making them more efficient than strings for keys and identifiers.
Example: :status, :id each is the most common iterator. It passes each element of a collection to a block.
Example:
[10, 20, 30].each { |n| puts n }
It returns the original collection. initialize is the constructor method called automatically when you create a new object with ClassName.new. It is used to set up instance variables.
Example:

def initialize(name)
  @name = name
end

Question 40 Ruby Programming

What does define_method do in Ruby?

case provides pattern-matching control flow:

case grade
when "A" then "Excellent"
when "B" then "Good"
when "C" then "Average"
else "Needs improvement"
end

It uses the === operator, so it works with ranges, classes, and regex too. Use File.read or File.open with a block:
content = File.read("file.txt")
Or line by line:
File.foreach("file.txt") { |line| puts line }
Using a block with File.open automatically closes the file. define_method dynamically creates an instance method at runtime.
Example:

class Dog
  ["sit", "stay"].each do |cmd|
    define_method(cmd) { puts cmd }
  end
end
Dog.new.sit # => "sit"

Both define blocks, but curly braces { } have higher precedence than do...end.
Convention: use { } for single-line blocks and do...end for multi-line blocks.

Question 41 Ruby Programming

What is the ampersand (&) operator for blocks?

The & operator converts between blocks and Procs:

&block in a parameter captures a block as a Proc.
&proc in a method call converts a Proc into a block.

Example:

def run(&blk)
  blk.call
end

Key differences:

Argument checking: Lambdas raise an error on wrong argument count; Procs assign nil to missing args.
Return behavior: return in a Lambda exits the lambda; return in a Proc exits the enclosing method.

A Gem is a packaged Ruby library or application distributed via RubyGems.
Install with: gem install rails
Manage project dependencies with a Gemfile and Bundler:
bundle install These are class macros that generate getter/setter methods:

attr_reader :name — getter only
attr_writer :name — setter only
attr_accessor :name — both getter and setter

They replace manually defining def name and def name=.

Question 42 Ruby Programming

What are frozen string literals in Ruby?

Adding # frozen_string_literal: true at the top of a Ruby file makes all string literals immutable by default. This improves performance by reducing object allocations and is a recommended practice in modern Ruby. Use begin...rescue...end:

begin
  risky_operation
rescue StandardError => e
  puts e.message
ensure
  cleanup
end

The ensure block always executes. A block is an anonymous chunk of code enclosed in do...end or curly braces { } that can be passed to a method.
Example:
[1,2,3].each { |n| puts n }

== — checks value equality (can be overridden).
eql? — checks value and type equality (used by Hash for keys).
equal? — checks object identity (same object_id).

Example: 1 == 1.0 # true, 1.eql?(1.0) # false

Question 43 Ruby Programming

What is a Mixin in Ruby?

Bundler manages gem dependencies for a Ruby project. It reads the Gemfile, resolves versions, and generates a Gemfile.lock.
Commands:

bundle install — install dependencies
bundle exec — run commands in the bundle context

A Mixin is a module included in a class to add shared behavior, providing a form of multiple inheritance.
Example:

module Greetable
  def greet
    "Hello!"
  end
end
class User
  include Greetable
end

Use File.open with the "w" mode:

File.open("out.txt", "w") do |f|
  f.puts "Hello, world!"
end

Use "a" mode to append instead of overwriting. The safe navigation operator &. calls a method only if the receiver is not nil, returning nil otherwise.
Example:
user&.name
This avoids NoMethodError on nil objects. Equivalent to user && user.name.

Question 44 Ruby Programming

What is the yield keyword in Ruby?

initialize is the constructor method called automatically when you create a new object with ClassName.new. It is used to set up instance variables.
Example:

def initialize(name)
  @name = name
end

yield transfers control from a method to the block passed to it.
Example:

def greet
  yield("World") if block_given?
end
greet { |name| puts "Hello, #{name}!" }

Class variables start with @@ and are shared among all instances of a class and its subclasses.
Example:
@@count = 0
Use with caution as subclasses share the same variable. A Hash is a collection of key-value pairs.
Examples:
h = { name: "Alice", age: 30 }
h = Hash.new(0)
Access values with h[:name].

Question 45 Ruby Programming

What is the difference between do...end and curly braces for blocks?

Embed expressions inside double-quoted strings with #{}:

name = "Ruby"
puts "Hello, #{name}!"
# => Hello, Ruby!

Single-quoted strings do not support interpolation. freeze makes an object immutable. Any attempt to modify a frozen object raises a FrozenError.
Example:

str = "hello"
str.freeze
str << " world" # => FrozenError

Check with str.frozen?.

== — checks value equality (can be overridden).
eql? — checks value and type equality (used by Hash for keys).
equal? — checks object identity (same object_id).

Example: 1 == 1.0 # true, 1.eql?(1.0) # false Both define blocks, but curly braces { } have higher precedence than do...end.
Convention: use { } for single-line blocks and do...end for multi-line blocks.

Question 46 Ruby Programming

What is Bundler in Ruby?

Use File.open with the "w" mode:

File.open("out.txt", "w") do |f|
  f.puts "Hello, world!"
end

Use "a" mode to append instead of overwriting. case provides pattern-matching control flow:

case grade
when "A" then "Excellent"
when "B" then "Good"
when "C" then "Average"
else "Needs improvement"
end

It uses the === operator, so it works with ranges, classes, and regex too. Bundler manages gem dependencies for a Ruby project. It reads the Gemfile, resolves versions, and generates a Gemfile.lock.
Commands:

bundle install — install dependencies
bundle exec — run commands in the bundle context

gsub replaces all occurrences matching a pattern:

"hello world".gsub(/[aeiou]/, "*")
# => "h*ll* w*rld"

You can also pass a block:
"cat bat".gsub(/\b\w/) { |m| m.upcase }

Question 47 Ruby Programming

What does block_given? do in Ruby?

Use the class keyword:

class Dog
  def initialize(name)
    @name = name
  end
  def bark
    "Woof!"
  end
end

block_given? returns true if a block was passed to the current method, false otherwise. It prevents a LocalJumpError when calling yield without a block.
Example:

def safe_call
  yield if block_given?
end

Both define blocks, but curly braces { } have higher precedence than do...end.
Convention: use { } for single-line blocks and do...end for multi-line blocks. yield transfers control from a method to the block passed to it.
Example:

def greet
  yield("World") if block_given?
end
greet { |name| puts "Hello, #{name}!" }

Question 48 Ruby Programming

What is metaprogramming in Ruby?

select returns a new array containing elements for which the block returns true.
Example:

[1,2,3,4,5].select { |n| n.even? }
# => [2, 4]

Inheritance lets a class derive behavior from a parent class using <.
Example:

class Dog < Animal
  def speak
    "Woof"
  end
end

Ruby supports single inheritance only. send invokes a method by name (as a symbol or string), including private methods.
Example:
obj.send(:my_method, arg1)
Use public_send to restrict to public methods only for safety. Metaprogramming is writing code that writes or modifies code at runtime. Ruby supports it extensively with methods like define_method, method_missing, and send.
It allows dynamic creation of methods, classes, and modules.

Question 49 Ruby Programming

How do you raise a custom exception in Ruby?

These are class macros that generate getter/setter methods:

attr_reader :name — getter only
attr_writer :name — setter only
attr_accessor :name — both getter and setter

They replace manually defining def name and def name=. An Array is an ordered collection created with square brackets or Array.new.
Examples:
nums = [1, 2, 3]
words = %w[hello world]
empty = Array.new(5, 0) A Mixin is a module included in a class to add shared behavior, providing a form of multiple inheritance.
Example:

module Greetable
  def greet
    "Hello!"
  end
end
class User
  include Greetable
end

Create a class inheriting from StandardError:

class MyError < StandardError; end
raise MyError, "Something went wrong"

Catch it with rescue MyError => e.

Question 50 Ruby Programming

How do you use string interpolation in Ruby?

Embed expressions inside double-quoted strings with #{}:

name = "Ruby"
puts "Hello, #{name}!"
# => Hello, Ruby!

Single-quoted strings do not support interpolation. Use begin...rescue...end:

begin
  risky_operation
rescue StandardError => e
  puts e.message
ensure
  cleanup
end

The ensure block always executes. Use File.read or File.open with a block:
content = File.read("file.txt")
Or line by line:
File.foreach("file.txt") { |line| puts line }
Using a block with File.open automatically closes the file. yield transfers control from a method to the block passed to it.
Example:

def greet
  yield("World") if block_given?
end
greet { |name| puts "Hello, #{name}!" }