How to make swapcase in Ruby 2.3 work with Cyrillic?

Question

ruby

How to make swapcase in Ruby 2.3 work with Cyrillic?

s = 'Строка'
print s.swapcase

Does not change character case.
Maybe take a different version of Ruby?

Answer 1

1) ruby ​​2.4+
2) Rails => s.mb_chars.swapcase.to_s
3) gems like unicode_utils