Ruby idiom to shortcircuit to return first non-nil using each and map

Question

This is the essence of what I'm trying to do but the 'break' doesn't feed right:

needle = nil
haystacks.each do |haystack|
  needle = haystack.look_for_needle()
  break if needle
end

This is shorter, but it will iterate over every haystack (without looking at least) even though it doesn't need to:

needle = nil
haystacks.each do |haystack|
  needle ||= haystack.look_for_needle()
end

This is a one-liner but (I believe) it is not lazy and so it does unnecessary work:

needle = hackstacks.map{|h| h.look_for_needle()}.detect{|x| !x.nil?}

I feel like there should be a one liner, but I'm not sure it would be:

needle = hackstacks.some_find_each_first_detect_lazy_map_thingee {|h| h.look_for_needle()}

Answer 1

With Ruby 2.x lazy enumerators:

needle = haystacks.lazy.map(&:look_for_needle).reject(&:nil?).first

Or:

needle = haystacks.lazy.map(&:look_for_needle).detect { |needle| !needle.nil? }

Or:

needle = haystacks.lazy.map(&:look_for_needle).detect(&:itself)