Class declaration syntax in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple Ruby class method call

What is the output of this Ruby code?

Ruby

class Greeter
  def greet
    "Hello, friend!"
  end
end

g = Greeter.new
puts g.greet

A Error: undefined method

B greet

C Greeter

D Hello, friend!

💡 Hint

Look at what the greet method returns and what puts does.

The greet method returns the string "Hello, friend!" and puts prints it to the screen.

❓ Predict Output

intermediate

Output when accessing an instance variable

What will this Ruby code print?

Ruby

class Person
  def initialize(name)
    @name = name
  end

  def name
    @name
  end
end

p = Person.new("Alice")
puts p.name

A Error: undefined variable

B Person

C Alice

D @name

💡 Hint

The initialize method sets @name, and the name method returns it.

The instance variable @name is set to "Alice" and returned by the name method, so puts prints "Alice".

🔧 Debug

advanced

Identify the error in this class declaration

What error does this Ruby code produce?

Ruby

class Animal
  def speak
    puts "Roar"
  end

  def speak
    puts "Meow"
  end
end

cat = Animal.new
cat.speak

A Output: Meow

B NoMethodError: undefined method 'speak' for Animal

C RuntimeError: method redefinition error

D SyntaxError: unexpected end-of-input, expecting keyword_end

💡 Hint

Check if all methods and classes are properly closed with 'end'.

The second speak method is missing an 'end', causing a syntax error due to incomplete method definition.

❓ Predict Output

advanced

Output of class variable usage

What is the output of this Ruby code?

Ruby

class Counter
  @@count = 0

  def initialize
    @@count += 1
  end

  def self.count
    @@count
  end
end

c1 = Counter.new
c2 = Counter.new
puts Counter.count

A 2

B 0

C 1

D Error: undefined class variable

💡 Hint

Class variables are shared among all instances.

Each new instance increments @@count by 1. After two instances, @@count is 2.

🧠 Conceptual

expert

Understanding inheritance and method overriding

Given these Ruby classes, what will be printed when calling d.speak?

Ruby

class Dog
  def speak
    "Woof"
  end
end

class LoudDog < Dog
  def speak
    super.upcase
  end
end

d = LoudDog.new
puts d.speak

A Woof

B WOOF

C super

D Error: undefined method 'upcase' for nil

💡 Hint

The 'super' keyword calls the parent method, then upcase changes the string.

LoudDog's speak calls Dog's speak with super, which returns "Woof", then upcase converts it to "WOOF".