An example using DelegateClass with core Classes. For the why, see: https://words.steveklabnik.com/beware-subclassing-ruby-core-classes

delegate_class.rb

class FerretString < String
  def to_s
    'Successfully overrode ...'
  end
end

class WombatString < DelegateClass(String)
  def initialize
    super('')
  end

  def to_s
    'Successfully overrode ...'
  end
end

ferret = FerretString.new
ferret << 'A ferret named "Mei" ...'

"#{ferret}"
#=> "A ferret named \"Mei\" ..."


wombat = WombatString.new
wombat << 'A wombat named "Zoe" ...'

"#{wombat}"
#=> "Successfully overrode ..."