[Solved] Given this Ruby code, what will be the output? hash = {a: [1, 2], b: [3, 4]} hash.freeze hash[:a] What does this tell us about freezing objects? | Ruby

Ruby - Class Methods and Variables

Given this Ruby code, what will be the output?

hash = {a: [1, 2], b: [3, 4]}
hash.freeze
hash[:a] << 5
puts hash[:a].inspect

What does this tell us about freezing objects?

ARuntimeError: can't modify frozen Hash

B[1, 2] - freeze prevents any changes including nested objects

C[1, 2, 5] - freeze prevents changing the hash keys but not the objects inside

DSyntaxError due to invalid hash modification

Step-by-Step Solution

Solution:

Step 1: Understand freezing the hash
The hash object is frozen, so its structure (keys and values) cannot be changed directly.
Step 2: Analyze modification of nested array
The value for key :a is an array, which is not frozen. Modifying this array with << 5 is allowed.
Step 3: Observe the output
The array now contains [1, 2, 5], showing that freezing the hash does not freeze nested objects.
Final Answer:
[1, 2, 5] - freeze prevents changing the hash keys but not the objects inside -> Option C
Quick Check:
Freeze is shallow = nested objects can change [OK]

Quick Trick: Freeze is shallow; nested objects stay mutable unless frozen [OK]

Common Mistakes:

Master "Class Methods and Variables" in Ruby

9 interactive learning modes - each teaches the same concept differently

More Ruby Quizzes

Given this Ruby code, what will be the output?