This article is part of the “Meta Advent 2019” series. I’ve committed to writing a new blog post here every day until Christmas.

So, we’ve made it to the final day of this year’s advent and to the final day of my “Meta Advent” blogging marathon! Time to examine another fun Ruby weirdness!

Most Rubyists probably know that they can use Array#* to “multiply” an array:1

arr = [1, 2, 3]
arr * 3 # => [1, 2, 3, 1, 2, 3, 1, 2, 3]

Nothing weird so far. Array#*, however, can do a bit more than this - its behaviour changes drastically when you pass a string instead of a number to it:

arr * " " => "1 2 3"
arr * "," => "1,2,3"

Seems now it behaves just like Array#join. Weird, right? I’d strong advise against using Array#* instead of Array#join, but it’s a cool little trick to know and a fine example of Ruby’s extreme flexibility.

That’s all I have for you today! Enjoy the holidays!

Articles in the Series

  1. I can’t remember when was the last time I needed to do something like this. ↩