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==========================
Interface Specifications
==========================
.. currentmodule:: zope.interface.interfaces
This document discusses the actual interface objects themselves. We
begin with a basic concept of specifying an object's behaviour (with
an `ISpecification`), and then we describe the way we write such a
specification (`IInterface`). Combinations of specifications (e.g., an
object that provides multiple interfaces) are covered by
`IDeclaration`.
Specification
=============
Specification objects implement the API defined by
:class:`ISpecification`:
.. autointerface:: ISpecification
:members:
:member-order: bysource
.. autoclass:: zope.interface.interface.Specification
:no-members:
For example:
.. doctest::
>>> from zope.interface.interface import Specification
>>> from zope.interface import Interface
>>> class I1(Interface):
... pass
>>> class I2(I1):
... pass
>>> class I3(I2):
... pass
>>> [i.__name__ for i in I1.__bases__]
['Interface']
>>> [i.__name__ for i in I2.__bases__]
['I1']
>>> I3.extends(I1)
True
>>> I2.__bases__ = (Interface, )
>>> [i.__name__ for i in I2.__bases__]
['Interface']
>>> I3.extends(I1)
False
Exmples for :meth:`.Specification.providedBy`:
.. doctest::
>>> from zope.interface import *
>>> class I1(Interface):
... pass
>>> @implementer(I1)
... class C(object):
... pass
>>> c = C()
>>> class X(object):
... pass
>>> x = X()
>>> I1.providedBy(x)
False
>>> I1.providedBy(C)
False
>>> I1.providedBy(c)
True
>>> directlyProvides(x, I1)
>>> I1.providedBy(x)
True
>>> directlyProvides(C, I1)
>>> I1.providedBy(C)
True
Examples for :meth:`.Specification.isOrExtends`:
.. doctest::
>>> from zope.interface import Interface
>>> from zope.interface.declarations import Declaration
>>> class I1(Interface): pass
...
>>> class I2(I1): pass
...
>>> class I3(Interface): pass
...
>>> class I4(I3): pass
...
>>> spec = Declaration()
>>> int(spec.extends(Interface))
1
>>> spec = Declaration(I2)
>>> int(spec.extends(Interface))
1
>>> int(spec.extends(I1))
1
>>> int(spec.extends(I2))
1
>>> int(spec.extends(I3))
0
>>> int(spec.extends(I4))
0
Examples for :meth:`.Specification.interfaces`:
.. doctest::
>>> from zope.interface import Interface
>>> class I1(Interface): pass
...
>>> class I2(I1): pass
...
>>> class I3(Interface): pass
...
>>> class I4(I3): pass
...
>>> spec = Specification((I2, I3))
>>> spec = Specification((I4, spec))
>>> i = spec.interfaces()
>>> [x.getName() for x in i]
['I4', 'I2', 'I3']
>>> list(i)
[]
Exmples for :meth:`.Specification.extends`:
.. doctest::
>>> from zope.interface import Interface
>>> from zope.interface.declarations import Declaration
>>> class I1(Interface): pass
...
>>> class I2(I1): pass
...
>>> class I3(Interface): pass
...
>>> class I4(I3): pass
...
>>> spec = Declaration()
>>> int(spec.extends(Interface))
1
>>> spec = Declaration(I2)
>>> int(spec.extends(Interface))
1
>>> int(spec.extends(I1))
1
>>> int(spec.extends(I2))
1
>>> int(spec.extends(I3))
0
>>> int(spec.extends(I4))
0
>>> I2.extends(I2)
False
>>> I2.extends(I2, False)
True
>>> I2.extends(I2, strict=False)
True
Interface
=========
Interfaces are a particular type of `ISpecification` and implement the
API defined by :class:`IInterface`.
Before we get there, we need to discuss two related concepts. The
first is that of an "element", which provides us a simple way to query
for information generically (this is important because we'll see that
``IInterface`` implements this interface):
..
IElement defines __doc__ to be an Attribute, so the docstring
in the class isn't used._
.. autointerface:: IElement
Objects that have basic documentation and tagged values.
Known derivatives include :class:`IAttribute` and its derivative
:class:`IMethod`; these have no notion of inheritance.
:class:`IInterface` is also a derivative, and it does have a
notion of inheritance, expressed through its ``__bases__`` and
ordered in its ``__iro__`` (both defined by
:class:`ISpecification`).
.. autoclass:: zope.interface.interface.Element
:no-members:
Next, we look at ``IAttribute`` and ``IMethod``. These make up the
content, or body, of an ``Interface``.
.. autointerface:: zope.interface.interfaces.IAttribute
.. autoclass:: zope.interface.interface.Attribute
:no-members:
.. autointerface:: IMethod
.. autoclass:: zope.interface.interface.Method
:no-members:
Finally we can look at the definition of ``IInterface``.
.. autointerface:: IInterface
.. autointerface:: zope.interface.Interface
Usage
-----
Exmples for :meth:`InterfaceClass.extends`:
.. doctest::
>>> from zope.interface import Interface
>>> class I1(Interface): pass
...
>>>
>>> i = I1.interfaces()
>>> [x.getName() for x in i]
['I1']
>>> list(i)
[]
|
