Is there a simpler way to check if a variable is `nil` or an empty array?

Question

I have a variable:

my_arr

which may be nil or an array. I would like to verify if it contains at least one element. It can be accomplished by:

my_arr && !my_arr.empty?

but I want to write it simpler. I tried:

!my_arr.empty?

but it fails if my_arr is nil. Is there a simple way?

There’s my_arr&.empty? == false, which is… not better. Also (my_arr || []).empty?, also not better. Just stick with what you have. — Ry-
– Ry- ♦, Commented Nov 9, 2017 at 22:49
Just make sure that my_arr is always an array. Why should something that is supposed to be an array actually be nil? — Stefan
– Stefan, Commented Nov 9, 2017 at 22:54

Stefan · Accepted Answer · 2017-11-09 23:05:39Z

3

This would work:

my_arr.to_a.empty?

Because:

nil.to_a #=> []

An array instance on the other hand just returns itself.

The same "trick" works for other classes:

nil.to_h.empty? #=> true
nil.to_s.empty? #=> true
nil.to_i.zero?  #=> true

answered Nov 9, 2017 at 23:05

Stefan

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Comments

souslov · Accepted Answer · 2017-11-09 22:56:43Z

1

You can use safe access operator and any? method in case your array can't possibly contain nil and false values:

my_arr&.any?

In case it can, you could use any?(&:to_s), which seems neither native nor more elegant than your original solution.

Generally it is a better idea to be sure that it is always going to be an array, or at least something with the same duck type support.

answered Nov 9, 2017 at 22:56

souslov

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