Class declaration syntax in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a class named Car.

Ruby

class [1]
end

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

Acar

BCar

Cvehicle

DClassCar

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase names for classes.

Using names that do not start with a capital letter.

The class name must start with a capital letter. Car is the correct class name.

2fill in blank

medium

Complete the code to define a method named start inside the class.

Ruby

class Car
  def [1]
    puts 'Car started'
  end
end

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

Arun

Bgo

Cbegin

Dstart

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different method name than requested.

Capitalizing method names (they should be lowercase).

The method name should be start as requested.

3fill in blank

hard

Fix the error in the class declaration by completing the blank.

Ruby

class [1]
  def initialize
    @speed = 0
  end
end

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

Avehicle

Bcar

CCar

Dspeed

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase class names.

Using variable names instead of class names.

Class names must start with a capital letter. Car is correct.

4fill in blank

hard

Fill both blanks to create a class Bike with a method ride that prints 'Riding'.

Ruby

class [1]
  def [2]
    puts 'Riding'
  end
end

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

ABike

BCar

Cride

Dstart

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up class and method names.

Using incorrect capitalization.

The class name is Bike and the method name is ride as requested.

5fill in blank

hard

Fill all three blanks to create a class Plane with a method fly that prints the speed stored in @speed.

Ruby

class [1]
  def [2]
    puts "Flying at #{ [3] } km/h"
  end
end

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

APlane

Bfly

C@speed

Dspeed

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the @ in instance variable.

Using wrong method or class names.

The class is Plane, method is fly, and the instance variable is @speed.

Practice

1. Which of the following is the correct way to start a class declaration in Ruby?

easy

A. class MyClass

B. Class myClass

C. def MyClass

D. module MyClass

Solution

1. Step 1: Recognize Ruby class syntax

   In Ruby, classes start with the keyword class followed by a capitalized name.

2. Step 2: Check each option

   class MyClass uses class and a capitalized name, which is correct. Options A, B, and D use wrong keywords or lowercase names.

3. Final Answer:

   class MyClass -> Option A

4. Quick Check:

   Class declaration starts with 'class' and capitalized name [OK]

Hint: Class names start with capital letter and use 'class' keyword [OK]

Common Mistakes:

• Using lowercase class names
• Using 'def' instead of 'class'
• Confusing 'module' with 'class'

2. Which of the following is the correct way to end a class declaration in Ruby?

easy

A. end

B. finish

C. stop

D. endclass

Solution

1. Step 1: Recall Ruby block endings

   Ruby uses the keyword end to close blocks like classes, methods, and conditionals.

2. Step 2: Identify correct ending keyword

   Only end uses end. The others are not valid Ruby keywords.

3. Final Answer:

   end -> Option A

4. Quick Check:

   Ruby blocks end with 'end' keyword [OK]

Hint: All Ruby blocks end with 'end' keyword [OK]

Common Mistakes:

• Using made-up keywords like 'stop' or 'finish'
• Writing 'endclass' instead of 'end'
• Omitting the 'end' keyword

3. What will be the output of this Ruby code?

class Dog
  def bark
    "Woof!"
  end
end

fido = Dog.new
puts fido.bark

medium

A. bark

B. Woof!

C. Dog

D. Error: undefined method

Solution

1. Step 1: Understand class and method

   The class Dog has a method bark that returns the string "Woof!".

2. Step 2: Create object and call method

   We create an object fido from Dog using new. Calling fido.bark returns "Woof!" which is printed.

3. Final Answer:

   Woof! -> Option B

4. Quick Check:

   Calling method returns its string output [OK]

Hint: Use .new to create object, call method to get output [OK]

Common Mistakes:

• Forgetting to use .new to create object
• Expecting method name instead of return value
• Confusing class name with method output

4. Identify the error in this Ruby class declaration:

class cat
  def meow
    "Meow!"
  end
end

medium

A. Missing 'end' keyword

B. Cannot use double quotes for strings

C. Method 'meow' should be outside the class

D. Class name should start with a capital letter

Solution

1. Step 1: Check class naming rules

   Ruby class names must start with a capital letter. Here, cat starts with lowercase.

2. Step 2: Verify other syntax

   The class has end keyword, method is inside class, and double quotes are valid for strings.

3. Final Answer:

   Class name should start with a capital letter -> Option D

4. Quick Check:

   Class names must be capitalized [OK]

Hint: Class names always start with uppercase letter [OK]

Common Mistakes:

• Using lowercase class names
• Thinking 'end' is missing
• Misplacing methods outside class

5. You want to create a class Car with a method start that returns "Engine started". Which code correctly declares this class and method?

hard

A. Car class
def start
"Engine started"
end
end

B. class car
def start
return Engine started
end
end

C. class Car
def start
"Engine started"
end
end

D. class Car
def start()
puts "Engine started"
end
end

Solution

1. Step 1: Check class declaration and naming

   class Car
     def start
       "Engine started"
     end
   end

   correctly uses class Car with capitalized name and ends with end.

2. Step 2: Check method definition and return value

   class Car
     def start
       "Engine started"
     end
   end

   defines method start returning the string "Engine started".

   class Car
     def start()
       puts "Engine started"
     end
   end

   uses puts which prints but returns nil, so not exactly the same.

3. Final Answer:

   class Car def start "Engine started" end end -> Option C

4. Quick Check:

   Class with capital name and method returning string [OK]

Hint: Class name capitalized; method returns string without puts [OK]

Common Mistakes:

• Using lowercase class names
• Using puts instead of return string
• Incorrect class declaration syntax