In #ror_au we were discussing using array.any? as a more elegant way of saying !array.empty?. As tempting as it is, its actually not a great idea. Read on for a better way…

So why does [].any? == ![].empty?

The underlying semantics of any? go

1. start with the result being false
2. iterate the array, switching the result to true if any elements are true
3. return the result

Consequently, if there are no elements at all false is returned.

This means that [].any? is false. Conveniently, this is the same result as ![].empty?, but looks nicer.

Unfortunately, Its only a coincidence that this degenerate case works.

! [nil].empty?   #=> true
! [false].empty? #=> true
[nil].any?       #=> false
[false].any?     #=> false

a better solution

Create a file RAILS_ROOT/lib/array_ext.rb.

class Array
  def full?
    !empty?
  end
end

If full? is too optimistic for your tastes, choose another word. I thought not_empty? sounded a bit crap.

Now hook it from your environment:

require 'array_ext'

Note that changes to this file won’t auto-reload in development mode. Restart your mongrels to see the change.

Look! identical semantics:

! [].empty?      #=> false
! [nil].empty?   #=> true
! [false].empty? #=> true

[].full?         #=> false
[nil].full?      #=> true
[false].full?    #=> true

Its definitely going to be slower than !empty?, but it could make your code look a lot nicer.