In Ruby, Enumerable#take_while does not include the element that ended the iteration. But sometimes, you may be interested in that element as well.

The trick is to use Enumerable#slice_after in combination with Enumerable#first instead:

p (1..10).slice_after { |i| i == 5 }.first || []
# => [1, 2, 3, 4, 5]

A few things to note:

  • The condition must be negated; that is, the predicate in slice_after is the opposite of the condition in take_while.
  • The || [] is necessary because slice_after returns an empty enumerator if the condition is never met.