Recently reading some posts about ruby, I found myself with this exciting method called lazy. This method will help us when looping over some objects: Array, Hashes, and Files. If you want to loop through a huge array, and we only want to select the first 20 elements that evaluate our criteria, this is the kind of job for our lazy method.

Without the use of lazy #

arr =  (1..1000).to_a
selected = []
arr.select do |x|
  selected << x if x.odd?
  break if selected.size > 20
end
p selected

With the use of lazy method #

arr =  (1..1000).to_a
selected = arr.lazy.select do |x|
  x if x.odd?
end.take(20).force
p selected

The syntax is more straightforward and is better in performance.