Hash as named parameters pattern in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of method using hash as named parameters

What is the output of this Ruby code using a hash as named parameters?

Ruby

def greet(options = {})
  "Hello, #{options[:name]}! You are #{options[:age]} years old."
end

puts greet(name: "Alice", age: 30)

A Hello, Alice! You are 30 years old.

B Hello, ! You are years old.

C Hello, {:name=>"Alice", :age=>30}! You are years old.

D SyntaxError

💡 Hint

Look at how the method accesses the hash keys inside the string.

The method greet takes a hash with keys :name and :age and inserts their values into the string. The output prints the greeting with the provided values.

🧠 Conceptual

intermediate

Understanding default values in hash named parameters

Given the method below, what will be the output of greet(name: "Bob")?

Ruby

def greet(options = {})
  name = options[:name] || "Guest"
  age = options[:age] || 25
  "Hello, #{name}! You are #{age} years old."
end

puts greet(name: "Bob")

A Hello, Bob! You are 25 years old.

B Hello, Guest! You are 25 years old.

C Hello, Bob! You are .

D Hello, ! You are 25 years old.

💡 Hint

Check how default values are assigned using || operator.

Since :age is not provided, the default 25 is used. The name is given as "Bob", so it is used directly.

🔧 Debug

advanced

Identify the error in hash named parameters usage

What error does this Ruby code raise when calling greet(name: "Eve")?

Ruby

def greet(options)
  "Hello, #{options[:name]}!"
end

greet(name: "Eve")

A ArgumentError: wrong number of arguments (given 1, expected 0)

B NoMethodError: undefined method `[]' for nil:NilClass

C No error, outputs: Hello, Eve!

D SyntaxError

💡 Hint

Check the method parameter and how the hash is passed.

The method expects one argument, a hash, and accesses the :name key correctly. The call passes a hash, so it works fine and outputs the greeting.

❓ Predict Output

advanced

Output when mixing positional and hash named parameters

What is the output of this Ruby code?

Ruby

def order(item, options = {})
  "Order: #{item}, Quantity: #{options[:quantity] || 1}, Price: #{options[:price] || 0}"
end

puts order("Book", quantity: 3, price: 15)

A ArgumentError: wrong number of arguments

B Order: Book, Quantity: , Price:

C Order: , Quantity: 3, Price: 15

D Order: Book, Quantity: 3, Price: 15

💡 Hint

Look at how the method uses a positional parameter and an optional hash.

The method receives "Book" as the first argument and a hash with quantity and price. It uses default values if keys are missing, but here both keys are present.

🧠 Conceptual

expert

How many keys in the hash after merging named parameters?

Consider this Ruby code. How many keys does the params hash have after merging?

Ruby

def process(params = {})
  defaults = {color: "red", size: "medium"}
  params = defaults.merge(params)
  params
end

result = process(size: "large", weight: "heavy")
puts result.keys.size

A 2

B 3

C 4

D 1

💡 Hint

Merging hashes combines keys, with later keys overwriting earlier ones.

The defaults hash has keys :color and :size. The params hash has :size and :weight. After merging, keys are :color, :size, and :weight, total 3 keys.