module ActiveSupport::Multibyte

Returns the current proxy class.

def self.proxy_class
  @proxy_class ||= ActiveSupport::Multibyte::Chars
end

ActiveSupport::Multibyte.proxy_class = CharsForUTF32

do this.
the ActiveSupport::Multibyte::Chars implementation for an example how to
to configure your own proxy class so you can support other encodings. See
The proxy class returned when calling mb_chars. You can use this accessor

def self.proxy_class=(klass)
  @proxy_class = klass
end