On: Why general inheritance is flawed and how to finally fix it

[MillenialMan]

I'd like languages to have some kind of "delegate" functionality, where you can just delegate names to point to nested names without screwing around with ownership - it would just act like a symlink. The scope of that action is limited and clear (and easy for your IDE to understand), and it's explicit that the subclass is still the "owner" of that property, which makes the whole thing a lot easier to navigate.

E.g. something like:

    class MyClass:
        def __init__(self, member_class):
            self.member_class = member_class

        # Delegate one member
        delegate move member_class.position.move

        # Delegate all members
        delegate * subclass.position.*             

Then:

    a.move == a.member_class.position.move

etc.

[kazinator → MillenialMan]

C++ can do something something like this (at compile time) in its -> operator (ancient feature, long before C++98 was standardized).

   obj->foo()

will expand into enough -> dereferences until a foo is found. For instance suppose the object returned by obj's operator ->() function doesn't have a foo member, but itself overloads ->. Then that overload will be used, and so on.

[nitroll → MillenialMan]

In Python you could do something like:

  class Base:
     def func(self):
         print("In Base.func:", self.name)
  
  class Child:
     def __init__(self, name):
         self.name = name
     func = Base.func
  
  c = Child("Foo")
  c.func() #=> In Base.func: Foo

[MillenialMan → nitroll]

The reason I'd like the construct is because it's explicit - intent (and the scope/limit of your intent) is encoded in what you create. It's clear you intend to do nothing with that name except symlink to the nested member, so the reader doesn't have to anticipate other behaviour (and can't accidentally do something else with it). Generic assignment doesn't convey the same restricted intent, and it doesn't carry those guard rails.

Really though it's a structure that only makes sense in strongly typed languages, so I probably shouldn't have used Python to illustrate the idea.