Quick Answer

Handle array boundary errors.

Understanding the Issue

Occurs when accessing array elements beyond valid indices.

The Problem

This code demonstrates the issue:

Ruby Error 
arr = [1, 2, 3]
arr[5] # Returns nil
arr.fetch(5) # IndexError

The Solution

Here's the corrected code:

Ruby Fixed 
# Solution 1: Check array length
index = 5
if index < arr.length
  arr[index]
end

# Solution 2: Use fetch with fallback
arr.fetch(5, "default")

# Solution 3: Safe navigation
arr.at(5)&.some_method

# Solution 4: Handle negative indices
arr[-1] # Last element
arr[-arr.length] # First element

Key Takeaways

Always validate array indices before access.