Redux: Circular Imports (Tim Cook)

Implementers (archive)
1

There's nothing wrong with a class defining a reference to another (or
the same) instance of that class - that's how most hierarchical OO
implementations would work.
I don't know Python - but other languages certainly won't worry about
this - it's not a circular reference in as much as the reference is (at
run time) to an instance of a class of the same type which may be the
same object, but generally would not be.

In the case of the thumbnail attribute it does mean a thumbnail can have
a thumbnail can have a thumbnail, for example - not likely but possible
in the model. Not circular but hierarchical.

For storing/retrieving there then needs to be implemented some mechanism
for 'walking' the structure from object to object - and if there is a
circular reference there, it needs to be dealt with (usually by flagging
each object as it is dealt with)

I'm not sure I read your email right, though - as you said you defined
ontology in IArchetype? Maybe I'm missing some Pythonism but I would
have had IArchetypeOntology implementing IArchetype, and
ArchetypeOntology implementing IArchetypeOntology

Eg in C#
    public interface IArchetype
  {}
  public class Archetype : IArchetype
  {}
  public interface IArchetypeOntology : IArchetype
  {
    Archetype ParentArchetype { get; set;}
  }
  public class ArchetypeOntology : IArchetypeOntology
  {
    private Archetype parentArchetype;
    public Archetype ParentArchetype
    {
      get
      {
        return parentArchetype;
      }
      set
      {
        parentArchetype = value;
      }
    }
  }

And I can have

      Archetype a = new Archetype();
      ArchetypeOntology b = new ArchetypeOntology();
      b.ParentArchetype = a;

Sorry if I have missed the point entirely - my first post;

Max