Comments and documentation in Ruby - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a single-line comment in Ruby.

Ruby

[1] This is a comment

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

A#

B!

C//

D--

Attempts:

3 left

💡 Hint

Common Mistakes

Using // or -- which are comment symbols in other languages.

Forgetting to add any symbol before the comment text.

In Ruby, single-line comments start with the # symbol.

2fill in blank

medium

Complete the code to add a multi-line comment using =begin and =end in Ruby.

Ruby

=begin
[1]
This is a multi-line comment.
=end

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

AIgnore this text

BThis is not a comment

CCode goes here

DThis is a comment

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving the text empty between =begin and =end.

Using code instead of comment text inside the block.

Text between =begin and =end is treated as a multi-line comment in Ruby.

3fill in blank

hard

Fix the error in the comment syntax below.

Ruby

[1]

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

A# This is a comment in Ruby

B-- This is a comment in Ruby

C/* This is a comment in Ruby */

D=begin This is a comment =end

Attempts:

3 left

💡 Hint

Common Mistakes

Using comment symbols from other languages like // or /* */.

Trying to use multi-line comment syntax for a single line.

Ruby uses # for single-line comments, not //.

4fill in blank

hard

Fill both blanks to create a method with a comment describing its purpose.

Ruby

# [1]
def greet(name)
  puts "Hello, #{name}!"
end

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

AThis method prints a message

BThis method greets a person

CThis method calculates sum

DThis method sorts a list

Attempts:

3 left

💡 Hint

Common Mistakes

Writing comments unrelated to the method's purpose.

Leaving the comment blank.

The comment describes that the method greets a person.

5fill in blank

hard

Fill all three blanks to add a multi-line comment explaining the code.

Ruby

=begin
[1]
[2]
[3]
=end
def add(a, b)
  a + b
end

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

AThis method adds two numbers

BIt takes two inputs

Cand returns their sum

DThis method multiplies two numbers

Attempts:

3 left

💡 Hint

Common Mistakes

Writing incorrect descriptions about the method.

Using single-line comment syntax inside multi-line comment block.

The multi-line comment explains the method's purpose, inputs, and output clearly.

Practice

1. What symbol is used to start a single-line comment in Ruby?

easy

A. #

B. //

C.

D. /*

Solution

1. Step 1: Identify single-line comment syntax in Ruby

   Ruby uses # to start a single-line comment.

2. Step 2: Compare with other options

   Options A, B, and C are comment symbols from other languages (JavaScript, HTML, C-style).

3. Final Answer:

   # -> Option A

4. Quick Check:

   Single-line comment = # [OK]

Hint: Single-line comments start with # in Ruby [OK]

Common Mistakes:

• Confusing Ruby comments with C-style or HTML comments
• Using // instead of #
• Trying to use /* */ for single-line comments

2. Which of the following is the correct way to write a multi-line comment in Ruby?

easy

A. //
This is a multi-line comment
//

B. /*
This is a multi-line comment
*/

C.

D. =begin
This is a multi-line comment
=end

Solution

1. Step 1: Recall Ruby multi-line comment syntax

   Ruby uses =begin and =end to mark multi-line comments.

2. Step 2: Check other options

   Options B, C, and D are multi-line comment styles from other languages (C, HTML, JavaScript).

3. Final Answer:

   =begin This is a multi-line comment =end -> Option D

4. Quick Check:

   Multi-line comment = =begin ... =end [OK]

Hint: Use =begin and =end for multi-line comments in Ruby [OK]

Common Mistakes:

• Using /* */ which is not valid in Ruby
• Using HTML style comments
• Trying to use // for multi-line comments

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

def greet(name)
  # This method returns a greeting message
  "Hello, #{name}!"
end

puts greet("Alice")

medium

A. greet

B. # This method returns a greeting message

C. Hello, Alice!

D. SyntaxError

Solution

1. Step 1: Understand the method and comment

   The comment line is ignored by Ruby and does not affect output. The method returns "Hello, #{name}!" with name replaced.

2. Step 2: Check the output of puts greet("Alice")

   It prints the string "Hello, Alice!" to the console.

3. Final Answer:

   Hello, Alice! -> Option C

4. Quick Check:

   Comment ignored, method returns greeting [OK]

Hint: Comments don't print; method returns greeting string [OK]

Common Mistakes:

• Thinking comments print output
• Confusing method name with output
• Expecting comment text to appear

4. Identify the error in this Ruby code snippet:

  =begin
This is a multi-line comment
# Another comment line
  =end
puts "Done"

medium

A. =begin and =end must be at the start of the line

B. The # inside multi-line comment causes error

C. Missing closing =end

D. Multi-line comment syntax is correct

Solution

1. Step 1: Check multi-line comment syntax rules

   In Ruby, =begin and =end must be at the start of the line with no leading spaces.

2. Step 2: Analyze the given code

   If =begin or =end are indented or not at line start, Ruby raises a syntax error.

3. Final Answer:

   =begin and =end must be at the start of the line -> Option A

4. Quick Check:

   Multi-line comment markers must start line [OK]

Hint: =begin and =end must start the line exactly [OK]

Common Mistakes:

• Indenting =begin or =end
• Thinking # inside multi-line comment causes error
• Forgetting to close multi-line comment

5. You want to document a Ruby method that takes a number and returns its square. Which comment style best describes the method's purpose and input/output?

hard

A. =begin
Squares a number
Input: num
Output: squared number
=end

B. # This method squares a number
# @param num [Integer] the number to square
# @return [Integer] the squared result

C. // Squares a number
// Input: num
// Output: squared number

D.

Solution

1. Step 1: Identify proper Ruby documentation comment style

   Ruby uses single-line comments with tags like @param and @return to document methods clearly.

2. Step 2: Compare options

   # This method squares a number # @param num [Integer] the number to square # @return [Integer] the squared result uses Ruby documentation style. =begin Squares a number Input: num Output: squared number =end uses multi-line comment but lacks tags. Options C and D use invalid comment styles for Ruby.

3. Final Answer:

   # This method squares a number # @param num [Integer] the number to square # @return [Integer] the squared result -> Option B

4. Quick Check:

   Use # with @param and @return for Ruby docs [OK]

Hint: Use # with @param and @return to document Ruby methods [OK]

Common Mistakes:

• Using multi-line comments without tags for documentation
• Using comment styles from other languages
• Not specifying input/output clearly