Instance methods in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define an instance method named greet inside the Person class.

Ruby

class Person
  def [1]
    puts "Hello!"
  end
end

Drag options to blanks, or click blank then click option'

Agreet

Bgreeting

Csay_hello

Dhello

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different method name than 'greet'.

Defining the method outside the class.

The method name should be greet as specified. This defines an instance method that can be called on Person objects.

2fill in blank

medium

Complete the code to call the instance method greet on the person object.

Ruby

person = Person.new
person.[1]

Drag options to blanks, or click blank then click option'

Agreeting

Bsay_hello

Chello

Dgreet

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a method name that does not exist.

Forgetting the dot before the method name.

To call the instance method greet, use person.greet.

3fill in blank

hard

Fix the error in the instance method definition by completing the method name correctly.

Ruby

class Animal
  def [1]
    puts "I am an animal"
  end
end

Drag options to blanks, or click blank then click option'

Aanimal_speak

BSpeak

Cspeak

Dspeak!

Attempts:

3 left

💡 Hint

Common Mistakes

Starting method name with uppercase letter.

Adding special characters to method names.

Method names in Ruby should start with a lowercase letter and speak is the correct conventional name here.

4fill in blank

hard

Fill both blanks to define an instance method age_in_dog_years that returns the age multiplied by 7.

Ruby

class Dog
  def [1]
    @age [2] 7
  end
end

Drag options to blanks, or click blank then click option'

Aage_in_dog_years

B*

C+

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition or subtraction instead of multiplication.

Incorrect method name.

The method name is age_in_dog_years and the multiplication operator * is used to multiply age by 7.

5fill in blank

hard

Complete the code to define an instance method full_name that returns the first and last name joined with a space.

Ruby

class User
  def [1]
    "#{@first_name} #{@last_name}"
  end
end

Drag options to blanks, or click blank then click option'

Afull_name

C+

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using + or - instead of space.

Forgetting the space between names.

The method full_name returns the first and last name joined by a space using string interpolation.

Practice

1.

What is an instance method in Ruby?

easy

A. A method that belongs to an object created from a class

B. A method that belongs to the class itself, not objects

C. A method that runs only once when the program starts

D. A method that cannot be called on any object

Solution

1. Step 1: Understand what instance methods are

   Instance methods are defined inside a class and belong to objects created from that class.

2. Step 2: Differentiate from class methods

   Class methods belong to the class itself, not to individual objects.

3. Final Answer:

   A method that belongs to an object created from a class -> Option A

4. Quick Check:

   Instance method = belongs to object [OK]

Hint: Instance methods belong to objects, not the class itself [OK]

Common Mistakes:

• Confusing instance methods with class methods
• Thinking instance methods run only once
• Believing instance methods cannot be called on objects

2.

Which of the following is the correct way to define an instance method greet inside a Ruby class Person?

class Person
  ?
end

easy

A. def self.greet; puts 'Hello'; end

B. def greet; puts 'Hello'; end

C. def Person.greet; puts 'Hello'; end

D. def greet() puts 'Hello' end

Solution

1. Step 1: Identify instance method syntax

   Instance methods are defined with def method_name inside the class without self..

2. Step 2: Check options

   def greet; puts 'Hello'; end uses correct syntax. def self.greet; puts 'Hello'; end and def Person.greet; puts 'Hello'; end define class methods. def greet() puts 'Hello' end misses semicolons or line breaks, causing syntax issues.

3. Final Answer:

   def greet; puts 'Hello'; end -> Option B

4. Quick Check:

   Instance method = def method_name [OK]

Hint: Instance methods use def without self. [OK]

Common Mistakes:

• Using self. which defines class methods
• Omitting semicolons or line breaks incorrectly
• Defining methods outside the class

3.

What will be the output of the following Ruby code?

class Dog
  def bark
    'Woof!'
  end
end

fido = Dog.new
puts fido.bark

medium

A. Dog

B. bark

C. Woof!

D. NoMethodError

Solution

1. Step 1: Understand the class and method

   The class Dog has an instance method bark that returns the string 'Woof!'.

2. Step 2: Trace the method call

   An object fido is created from Dog, then fido.bark calls the bark method, returning 'Woof!'.

3. Final Answer:

   Woof! -> Option C

4. Quick Check:

   Calling instance method returns 'Woof!' [OK]

Hint: Instance method returns its string when called on object [OK]

Common Mistakes:

• Expecting method name instead of return value
• Confusing class name with output
• Thinking method is undefined

4.

Find the error in this Ruby code and select the fix that will make it work:

class Cat
  def meow
    puts 'Meow!'
  end
end

kitty = Cat.new
kitty.meow()

medium

A. Remove parentheses from kitty.meow() to kitty.meow

B. Change def meow to def self.meow

C. Add return before puts in method

D. No error; code works as is

Solution

1. Step 1: Check method definition and call

   The method meow is defined correctly as an instance method and called on an object.

2. Step 2: Verify syntax and usage

   Using parentheses in method call is allowed in Ruby, so kitty.meow() is valid.

3. Final Answer:

   No error; code works as is -> Option D

4. Quick Check:

   Parentheses optional in method calls [OK]

Hint: Parentheses optional in Ruby method calls [OK]

Common Mistakes:

• Thinking parentheses cause errors
• Confusing instance and class methods
• Adding unnecessary return before puts

5.

Given the class below, what will puts user.full_name print?

class User
  def initialize(first, last)
    @first_name = first
    @last_name = last
  end

  def full_name
    "#{@first_name} #{@last_name}".upcase
  end
end

user = User.new('Jane', 'Doe')

hard

A. JANE DOE

B. Error: undefined method full_name

C. "Jane Doe"

D. Jane Doe

Solution

1. Step 1: Understand instance variables and method

   The initialize method sets @first_name and @last_name. The full_name method returns their combination in uppercase.

2. Step 2: Trace the method call

   Calling user.full_name returns "JANE DOE" because of the upcase method.

3. Final Answer:

   JANE DOE -> Option A

4. Quick Check:

   full_name returns uppercase full name [OK]

Hint: String interpolation with upcase changes output to uppercase [OK]

Common Mistakes:

• Ignoring upcase method effect
• Expecting original case output
• Confusing string quotes in output