Open struct for dynamic objects in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this OpenStruct code?

Consider this Ruby code using OpenStruct. What will it print?

Ruby

require 'ostruct'
person = OpenStruct.new(name: 'Alice', age: 30)
puts person.name
puts person.age

A name\nage

B Error: undefined method 'name'

C nil\nnil

D Alice\n30

💡 Hint

OpenStruct allows you to access keys as methods.

OpenStruct creates an object with attributes from the hash keys. You can call them like methods to get their values.

❓ Predict Output

intermediate

What happens when you add a new attribute dynamically?

What will this Ruby code print?

Ruby

require 'ostruct'
obj = OpenStruct.new
obj.color = 'red'
puts obj.color

A red

B color

C nil

D NoMethodError

💡 Hint

OpenStruct allows adding new attributes by assignment.

You can add new attributes to an OpenStruct object by assigning to them. Then you can read them back as methods.

🔧 Debug

advanced

Why does this OpenStruct code raise an error?

This code raises an error. What is the cause?

Ruby

require 'ostruct'
obj = OpenStruct.new
puts obj.size

A Returns 0 because OpenStruct is empty

B Returns nil because attribute is missing

C NoMethodError because 'size' is not defined

D SyntaxError due to missing attribute

💡 Hint

OpenStruct only has methods for keys you set.

Calling a method that was never set as an attribute on OpenStruct returns nil.

❓ Predict Output

advanced

What is the output of nested OpenStruct objects?

What will this Ruby code print?

Ruby

require 'ostruct'
address = OpenStruct.new(city: 'Paris', zip: '75000')
user = OpenStruct.new(name: 'Bob', address: address)
puts user.address.city

A Paris

B city

C nil

D NoMethodError

💡 Hint

OpenStruct objects can be nested as attribute values.

The 'address' attribute is itself an OpenStruct, so you can call city on it.

🧠 Conceptual

expert

How does OpenStruct store its data internally?

Which statement best describes how OpenStruct stores its attributes internally?

A It uses a database to store attributes persistently.

B It stores attributes as instance variables with fixed names.

C It stores attributes in a hash and defines methods dynamically for each key.

D It stores attributes in an array indexed by insertion order.

💡 Hint

Think about how OpenStruct allows dynamic method calls for keys.

OpenStruct keeps a hash of attributes and dynamically defines getter and setter methods for each key.