Question

With strings one can do this:

a = "hello"
a.upcase!
p a #=> "HELLO"

But how would I write my own method like that?

Something like (although that doesn’t work obviously):

class MyClass
  def positify!
    self = [0, self].max
  end
end

I know there are some tricks one can use on String but what if I’m trying to do something like this for Object?

Answer 1

Well, the upcase! method doesn’t change the object identity, it only changes its internal structure (s.object_id == s.upcase!.object_id).

On the other hand, numbers are immutable objects and therefore, you can’t change their value without changing their identity. AFAIK, there’s no way for an object to self-change its identity, but, of course, you may implement positify! method that changes properties of its object – and this would be an analogue of what upcase! does for strings.