Python, Zope Component Architecture, Adapter Registration

Question

In a standalone python application, I use zope.interface, zope.component packages to register and access application adapters. I thought I could use the concept of a metaclass to register adapters from within the init method of the metaclass. This “automates” the adapter registration process. You see problems with this approach, for example. using the attributes that the zope package adds to the class? Thank you in advance for your entry.

from zope import component
from zope.interface import Interface, implements


class MetaclassAdapter(type):
    def __init__(cls, clsname, bases, attrs):
        super(MetaclassAdapter, cls).__init__(clsname, bases, attrs)
        component.provideAdapter(cls, cls.__component_adapts__, cls.__implements_advice_data__[0][0])


class IDocument(Interface):
  """Document interface."""

  def title():
    pass

  def author():
    pass

  def content():
    pass

class IPrinter(Interface):
  """Printer interface."""

  def write():
    """Print instance to ..."""


class Printer(object):
  """Adapt instances that provide IDocument interface to IPrinter.
  Print document attributes to stdout.
  """

  __metaclass__ = MetaclassAdapter
  implements(IPrinter)
  component.adapts(IDocument)

  def __init__(self, context):
    """Store adapted instance that provides IDocument."""
    self.context = context

  def write(self):
    """Serialize document."""
    print 'author: ', self.context.author()
    print 'title: ', self.context.title()
    print 'content: ', self.context.content()



class TextDocument(object):
  implements(IDocument)

  def __init__(self, author, title, content):
    self._author = author
    self._title = title
    self._content = content

  def title(self):
    return self._title

  def author(self):
    return self._author

  def content(self):
    return self._content

# Create instance of TextDocument and store / serialize it to...
IPrinter(TextDocument("Leo T.", "Short Stories", "Once upon a time...")).write()

Answer 1

Just because you can, it does not mean that you should.

- , , . , .

Answer 2

: @Tobu, . , . , zope.interface.implements metaclass shuffle .

, , , . Adapter, , :

class MetaclassAdapter(type):
    def __init__(cls, clsname, bases, attrs):
        super(MetaclassAdapter, cls).__init__(clsname, bases, attrs)
        component.provideAdapter(cls)

, ( ), , , .

registerAdapter keyword = keyword. API- intopepection zope.interface(zope.interfaces.implementedBy), , .