Map an array modifying only elements matching a certain condition

Question

In Ruby, what is the most expressive way to map an array in such a way that certain elements are modified and the others left untouched?

This is a straight-forw

Answer 1

Ruby 2.7+

As of 2.7 there's a definitive answer.

Ruby 2.7 is introducing filter_map for this exact purpose. It's idiomatic and performant, and I'd expect it to become the norm very soon.

For example:

numbers = [1, 2, 5, 8, 10, 13]
enum.filter_map { |i| i * 2 if i.even? }
# => [4, 16, 20]

Here's a good read on the subject.

Hope that's useful to someone!