How to Reverse an Array in Ruby: Simple Syntax and Examples

In Ruby, you can reverse an array using the reverse method which returns a new array with elements in reverse order. To reverse the array in place, use reverse! which modifies the original array.

Syntax

The reverse method returns a new array with the elements reversed, leaving the original array unchanged. The reverse! method reverses the elements of the array in place, changing the original array.

ruby

array.reverse
array.reverse!

Example

This example shows how to use reverse to get a reversed copy of the array and reverse! to reverse the array itself.

ruby

array = [1, 2, 3, 4, 5]

reversed_array = array.reverse
puts "Reversed copy: #{reversed_array.inspect}"
puts "Original array after reverse: #{array.inspect}"

array.reverse!
puts "Original array after reverse!: #{array.inspect}"

Output

Reversed copy: [5, 4, 3, 2, 1]
Original array after reverse: [1, 2, 3, 4, 5]
Original array after reverse!: [5, 4, 3, 2, 1]

Common Pitfalls

A common mistake is expecting reverse to change the original array. It only returns a new reversed array. To modify the original array, you must use reverse!. Forgetting the exclamation mark means the original array stays the same.

ruby

array = [10, 20, 30]

# Wrong: This does not change the original array
array.reverse
puts array.inspect  # Output: [10, 20, 30]

# Right: This changes the original array
array.reverse!
puts array.inspect  # Output: [30, 20, 10]

Output

[10, 20, 30]
[30, 20, 10]

Quick Reference

• array.reverse: Returns a new reversed array, original unchanged.
• array.reverse!: Reverses the array in place, modifying the original.

Key Takeaways

Use reverse to get a reversed copy without changing the original array.

Use reverse! to reverse the array itself and modify it.

Remember reverse does not change the original array, only returns a new one.

For in-place reversal, always use reverse! with the exclamation mark.

Check your array after reversal to confirm if it was changed or not.