Ruby style guide essentials - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Ruby code snippet?

Consider the following Ruby code. What will it print?

Ruby

def greet(name)
  puts "Hello, #{name.capitalize}!"
end

greet("alice")

A Hello, Alice!

B Hello, alice!

C hello, Alice!

D HELLO, ALICE!

💡 Hint

Look at the capitalize method and how it changes the string.

The capitalize method makes the first letter uppercase and the rest lowercase. So "alice" becomes "Alice".

🧠 Conceptual

intermediate

Which is the preferred Ruby style for method names?

According to Ruby style guide essentials, which method name style is preferred?

A PascalCaseMethod

B snake_case_method

C camelCaseMethod

D kebab-case-method

💡 Hint

Think about how Ruby methods are usually named to improve readability.

Ruby style guide recommends using snake_case for method names for clarity and consistency.

🔧 Debug

advanced

What error does this Ruby code raise?

Examine the code below. What error will it raise when run?

Ruby

numbers = [1, 2, 3]
puts numbers[3].to_s

A NilClass error

B IndexError

C No error, prints empty string

D NoMethodError

💡 Hint

What does Ruby return when accessing an array index that is out of range?

Accessing an out-of-range index returns nil. Calling to_s on nil returns an empty string, so no error occurs.

📝 Syntax

advanced

Which option correctly defines a Ruby class with an initialize method?

Choose the correct Ruby syntax for defining a class Person with an initialize method that takes a name parameter.

A

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

B

class Person
  def initialize name
    name = @name
  end
end

C

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

D

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

💡 Hint

Remember Ruby uses def and end to define methods and classes, and instance variables start with @.

Option A correctly defines the class and initialize method, assigns the parameter to an instance variable, and closes all blocks properly.

🚀 Application

expert

How many key-value pairs are in the resulting hash?

What is the number of key-value pairs in the hash created by this Ruby code?

Ruby

hash = { a: 1, b: 2, a: 3, c: 4 }

A 4

B 1

C 2

D 3

💡 Hint

Consider what happens when a hash has duplicate keys.

In Ruby, if a hash has duplicate keys, the last value for that key overwrites previous ones. So keys are :a, :b, :c with values 3, 2, 4 respectively, total 3 pairs.

Practice

1. According to the Ruby style guide essentials, which naming convention should you use for method names?

easy

A. snake_case

B. CamelCase

C. kebab-case

D. PascalCase

Solution

1. Step 1: Understand method naming conventions

   Ruby style guide recommends using snake_case for method names to improve readability.

2. Step 2: Compare options with style guide

   CamelCase and PascalCase are used for classes and modules, not methods.

3. Final Answer:

   snake_case -> Option A

4. Quick Check:

   Method names use snake_case [OK]

Hint: Methods and variables use snake_case, classes use CamelCase [OK]

Common Mistakes:

• Using CamelCase for method names
• Using kebab-case which is invalid in Ruby
• Confusing class naming with method naming

2. Which of the following is the correct way to indent Ruby code according to the style guide?

easy

A. 2 spaces

B. 4 spaces

C. 1 tab

D. No indentation

Solution

1. Step 1: Recall indentation rules

   The Ruby style guide specifies using 2 spaces for indentation to keep code clean and consistent.

2. Step 2: Evaluate options

   4 spaces and tabs are common in other languages but not recommended in Ruby style guide.

3. Final Answer:

   2 spaces -> Option A

4. Quick Check:

   Indent with 2 spaces [OK]

Hint: Always indent Ruby code with 2 spaces, never tabs [OK]

Common Mistakes:

• Using tabs instead of spaces
• Using 4 spaces like in Python or JavaScript
• No indentation causing unreadable code

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

class MyClass
  def greet
    name = 'Alice'
    puts "Hello, #{name}!"
  end
end

obj = MyClass.new
obj.greet

medium

A. SyntaxError

B. Hello, #{name}!

C. Hello, name!

D. Hello, Alice!

Solution

1. Step 1: Understand string interpolation

   Double quotes allow #{name} to be replaced by the variable's value, which is 'Alice'.

2. Step 2: Trace method call and output

   Calling greet prints "Hello, Alice!" to the console.

3. Final Answer:

   Hello, Alice! -> Option D

4. Quick Check:

   Double quotes enable interpolation = Hello, Alice! [OK]

Hint: Double quotes allow #{var} interpolation, single quotes do not [OK]

Common Mistakes:

• Using single quotes expecting interpolation
• Confusing variable name with string literal
• Expecting syntax error from interpolation

4. Identify the style error in the following Ruby code snippet:

class my_class
  def say_hello
    puts 'Hello world'
  end
end

medium

A. Class name should be snake_case

B. Method name should be CamelCase

C. Class name should be CamelCase

D. String should use double quotes

Solution

1. Step 1: Check class naming conventions

   Ruby style guide requires class names to use CamelCase, not snake_case.

2. Step 2: Verify method and string style

   Method name is correctly snake_case; single quotes are allowed if no interpolation needed.

3. Final Answer:

   Class name should be CamelCase -> Option C

4. Quick Check:

   Classes use CamelCase [OK]

Hint: Classes and modules use CamelCase, not snake_case [OK]

Common Mistakes:

• Using snake_case for class names
• Changing method names to CamelCase incorrectly
• Forcing double quotes when not needed

5. You want to define a Ruby method that returns a greeting with a name variable. Which style is best according to the Ruby style guide essentials?

def greetUser(name)
  return 'Hello, ' + name + '!'
end

hard

A. def greetUser(name)
"Hello, #{name}!"
end

B. def greet_user(name)
"Hello, #{name}!"
end

C. def greet_user(name)
'Hello, ' + name + '!'
end

D. def greetUser(name)
'Hello, ' + name + '!'
end

Solution

1. Step 1: Apply method naming conventions

   Method names should use snake_case, so greet_user is correct.

2. Step 2: Use string interpolation with double quotes

   Double quotes allow cleaner string interpolation instead of concatenation.

3. Final Answer:

   def greet_user(name) "Hello, #{name}!" end -> Option B

4. Quick Check:

   snake_case + interpolation = def greet_user(name) "Hello, #{name}!" end [OK]

Hint: Use snake_case for methods and double quotes for interpolation [OK]

Common Mistakes:

• Using CamelCase for method names
• Using single quotes with interpolation expecting it to work
• Concatenating strings instead of interpolation