如何以编程方式识别数组的结尾

Question

对于数组[1, 2, 3, 4],，当我处理每个元素时，如何知道我在数组的最后一个元素上。

arr = [1, 2, 3, 4]
arr.each do |a|

...

end

Answer 1

arr = [1, 2, 3, 4]
l = arr.length - 1
arr.each_with_index do |a, i|
  if i == l
    ...
  else
    ...
  end
end

Answer 2

arr = [1, 2, 3, 4]
arr.each_with_index do |el, idx|
  if idx == arr.length - 1
    # you're on the last element
  end
end