What is the opposite method of Array.empty? or [].empty? in ruby

No single method I know of is going to give you that in Ruby. Key word 'single':

[5].size.positive? => true
[5].size.nonzero? => 1

[].size.positive? => false
[].size.nonzero? => nil

Both of these are even more useful with the safe navigation operator, since nil returns falsy, meaning negative methods (like #empty?) break down a bit:

# nil considered 'not empty' isn't usually what you want
not_empty = proc{|obj| !obj&.empty? }

not_empty.call nil => true
not_empty.call [ ] => false
not_empty.call [5] => true


# gives different 3 answers for the 3 cases
# gives truthy/falsy values you'd probably expect
positive_size = proc{|obj| obj&.size&.positive? }

positive_size.call nil => nil
positive_size.call [ ] => false
positive_size.call [5] => true


# gives truthy/falsy values you'd probably expect
nonzero_size = proc{|obj| obj&.size&.nonzero? }

nonzero_size.call nil => nil
nonzero_size.call [ ] => nil
nonzero_size.call [5] => 1