YARD for documentation in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is YARD in Ruby?

YARD is a tool for writing and generating documentation for Ruby code. It helps you create clear, organized docs from special comments in your code.

beginner

How do you write a basic YARD comment for a method?

You write a comment starting with # before the method, using tags like @param for parameters and @return for the return value.

beginner

What does the @param tag do in YARD?

The @param tag describes a method parameter. It shows the parameter name, type, and a short explanation.

beginner

How do you generate HTML documentation using YARD?

Run the command yard doc in your terminal. It creates HTML files you can open in a browser to read your docs.

beginner

Why is documenting code with YARD helpful?

It makes your code easier to understand for others and yourself later. It also helps tools and editors show useful info about your code.

What symbol starts a YARD comment in Ruby?

A //

B /*

C <!--

D #

YARD comments in Ruby start with the # symbol, just like regular Ruby comments.

Which YARD tag describes a method's return value?

A @return

B @param

C @yield

D @example

The @return tag explains what a method returns.

How do you generate documentation files with YARD?

A yard doc

B yard build

C yard make

D yard generate

The command yard doc creates the documentation files.

What is the main purpose of YARD?

A Run Ruby programs

B Document Ruby code

C Format Ruby code

D Debug Ruby code

YARD is used to write and generate documentation for Ruby code.

Which tag would you use to describe a method parameter's type?

A @arg

B @type

C @param

D @input

The @param tag includes the parameter name and type.

Explain how to write a YARD comment for a method that takes two parameters and returns a value.

Think about describing inputs and outputs clearly.

Describe the steps to generate and view documentation using YARD.

Focus on the process from code to readable docs.

Practice

1. What is the main purpose of using YARD in Ruby code?

easy

A. To automatically fix syntax errors in Ruby code

B. To speed up the execution of Ruby programs

C. To write clear documentation inside the code using special comments

D. To convert Ruby code into other programming languages

Solution

1. Step 1: Understand YARD's role

   YARD is a tool to add documentation inside Ruby code using comments.

2. Step 2: Identify the correct purpose

   It helps explain code clearly, not speed execution or fix errors.

3. Final Answer:

   To write clear documentation inside the code using special comments -> Option C

4. Quick Check:

   YARD -> documentation [OK]

Hint: YARD is for documentation, not code execution [OK]

Common Mistakes:

• Thinking YARD runs or speeds up code
• Confusing YARD with debugging tools
• Assuming YARD converts code to other languages

2. Which of the following is the correct way to document a method parameter using YARD?

easy

A. # @param name [String] the user's name

B. // @param name String the user's name

C. /* @param name String the user's name */

D.

Solution

1. Step 1: Recognize Ruby comment style

   Ruby uses # for single-line comments, so YARD tags must start with #.

2. Step 2: Identify correct YARD tag syntax

   The correct format is "# @param name [Type] description".

3. Final Answer:

   # @param name [String] the user's name -> Option A

4. Quick Check:

   # -> Ruby comments [OK]

Hint: YARD tags start with # in Ruby code comments [OK]

Common Mistakes:

• Using comment styles from other languages
• Omitting square brackets around type
• Writing tags inside HTML or block comments

3. What will be the output of the following YARD comment when generating documentation?

# Adds two numbers
# @param a [Integer] first number
# @param b [Integer] second number
# @return [Integer] sum of a and b
# @example
#   add(2, 3) #=> 5
def add(a, b)
  a + b
end

medium

A. Only the method name will appear without any details

B. Syntax error because @example is not allowed

C. The code will run and print 5

D. Documentation showing method description, parameters with types, return type, and example usage

Solution

1. Step 1: Understand YARD comment tags

   The tags @param, @return, and @example describe method details for documentation.

2. Step 2: Recognize YARD output

   YARD generates HTML docs showing description, parameters, return type, and examples.

3. Final Answer:

   Documentation showing method description, parameters with types, return type, and example usage -> Option D

4. Quick Check:

   YARD tags -> detailed docs [OK]

Hint: YARD tags create detailed docs, not runtime output [OK]

Common Mistakes:

• Confusing documentation comments with code execution
• Thinking @example causes errors
• Expecting code output instead of docs

4. Identify the error in this YARD comment block:

# @param name String the user's name
# @return String greeting message
def greet(name)
  "Hello, #{name}!"
end

medium

A. Missing square brackets around the type in @param and @return tags

B. The method name should be capitalized

C. YARD comments must be placed after the method definition

D. The string interpolation syntax is incorrect

Solution

1. Step 1: Check YARD tag syntax

   YARD requires types in square brackets, e.g., [String], not just String.

2. Step 2: Verify other parts

   Method name capitalization and comment placement are correct; string interpolation is valid Ruby.

3. Final Answer:

   Missing square brackets around the type in @param and @return tags -> Option A

4. Quick Check:

   [Type] -> YARD requirement [OK]

Hint: Always put types in square brackets in YARD tags [OK]

Common Mistakes:

• Omitting square brackets around types
• Placing comments after method instead of before
• Confusing Ruby syntax errors with documentation errors

5. You want to document a Ruby class with YARD that has a method returning a hash with keys as symbols and values as arrays of strings. Which is the best way to write the @return tag for this method?

hard

A. # @return [Hash] a hash with keys and values

B. # @return [Hash{Symbol => Array<String>}] a hash mapping symbols to arrays of strings

C. # @return [Array<Hash>] an array of hashes

D. # @return [Hash(Symbol, Array)] a hash with symbol keys and array values

Solution

1. Step 1: Understand complex type syntax in YARD

   YARD supports detailed type annotations like Hash{KeyType => ValueType}.

2. Step 2: Match the method return type

   The method returns a hash with Symbol keys and Array of String values, so use Hash{Symbol => Array<String>}.

3. Final Answer:

   # @return [Hash{Symbol => Array<String>}] a hash mapping symbols to arrays of strings -> Option B

4. Quick Check:

   Hash{Key => Value} -> correct syntax [OK]

Hint: Use Hash{KeyType => ValueType} for detailed return types [OK]

Common Mistakes:

• Using vague types like just Hash
• Incorrect syntax like Hash(Symbol, Array)
• Confusing array of hashes with hash of arrays