Immutable data with freeze in Ruby - Mini Project: Build & Apply

Immutable data with freeze

📖 Scenario: You are working on a simple Ruby program that manages a list of favorite fruits. To avoid accidental changes to this list later in the program, you want to make the list immutable.

🎯 Goal: Create a frozen array of fruits so that the list cannot be changed after creation. Then, try to add a new fruit to see what happens.

📋 What You'll Learn

Create an array called fruits with the exact values 'apple', 'banana', and 'cherry'

Create a variable called immutable_fruits that holds the frozen version of fruits

Attempt to add 'orange' to immutable_fruits using the push method

Print the immutable_fruits array

💡 Why This Matters

🌍 Real World

Freezing data helps prevent accidental changes in programs, which is important in many real-world applications like configuration settings or constant values.

💼 Career

Understanding immutability and error handling is useful for writing safer, more reliable Ruby code in software development jobs.

1

Create the initial array of fruits

Create an array called fruits with the exact values 'apple', 'banana', and 'cherry'.

Ruby

# Create the array fruits with 'apple', 'banana', and 'cherry'
# Your code here

Need a hint?

Use square brackets [] to create an array and separate items with commas.

2

Freeze the array to make it immutable

Create a variable called immutable_fruits that holds the frozen version of the fruits array using the freeze method.

Ruby

fruits = ['apple', 'banana', 'cherry']
# Freeze the fruits array and assign it to immutable_fruits
# Your code here

Need a hint?

Use freeze method on the array to make it immutable.

3

Try to add a new fruit to the frozen array

Use the push method to try to add 'orange' to the immutable_fruits array.

Ruby

fruits = ['apple', 'banana', 'cherry']
immutable_fruits = fruits.freeze
# Try to add 'orange' to immutable_fruits
# Your code here

Need a hint?

Use push method on immutable_fruits. Wrap it in begin...rescue to catch the error.

4

Print the frozen array and error message

Print the immutable_fruits array and then print the error_message variable to show the error caused by trying to modify the frozen array.

Ruby

fruits = ['apple', 'banana', 'cherry']
immutable_fruits = fruits.freeze
begin
  immutable_fruits.push('orange')
rescue => e
  error_message = e.message
end
# Print immutable_fruits and error_message
# Your code here

Need a hint?

Use puts to print the array and the error message. Use inspect to show the array nicely.