How do you select every nth item in an array?

Question

I'm looking to find a way in Ruby to select every nth item in an array. For instance, selecting every second item would transform:

["cat", "dog", "mouse", "tiger"] 

into:

["dog", "tiger"] 

Is there a Ruby method to do so, or is there any other way to do it?

I tried using something like:

[1,2,3,4].select {|x| x % 2 == 0} # results in [2,4] 

but that only works for an array with integers, not strings.

Answer 1

You can use Enumerable#each_slice:

["cat", "dog", "mouse", "tiger"].each_slice(2).map(&:last) # => ["dog", "tiger"] 

Update:

As mentioned in the comment, last is not always suitable, so it could be replaced by first, and skipping first element:

["cat", "dog", "mouse", "tiger"].drop(1).each_slice(2).map(&:first) 

Unfortunately, making it less elegant.

IMO, the most elegant is to use .select.with_index, which Nakilon suggested in his comment:

["cat", "dog", "mouse", "tiger"].select.with_index{|_,i| (i+1) % 2 == 0}