Understanding Zope Component Architecture and Component Dependency

Question

It's quite difficult to have a good title of my question. From what I understand, the Adapter is to add more services to the components without changing it. The adapter can extends services from multiple components.

But what about the dependency between component? How can I set the dependency between the component A (Person) and the component B (Task) like this normal Python code

class Person:
 pass

class Task:
 def __init__(self, person):
  self.owner = person

If I implements the 2 classes

from zope.interface import Interface
from zope.interface import implements

class IPerson(Interface):
 pass

class Person(object):
 implements(IPerson)

class ITask(Interface):
 pass

class Task(object):
 implements(ITask)
 def __init__(self, person):
  self.owner = person

Is it a good implementation?

Answer 1

The point is that with the ZCA, you don't set a dependency to a concrete object. You use utilities instead.

Object A would implement an interface, and you look up the interface in B to find a concrete implementation, which could be A, but that depends on the register.

Note that the ZCA is meant to allow you to plug different implementations for a given interface, and is not always needed.

If your Task object expects a specific type, then document that. Using the ZCA is not a requirement here. At most, you can try to adapt the passed in value to IPerson; if the passed in object already implements that interface, that action is a no-op:

class Task(object):
    implements(ITask)

    def __init__(self, owner):
        self.owner = IPerson(owner)

That would allow you the flexibility of passing in something else later, something that is not a Person itself, but could be adapted to that interface.