Text File
sources.txt

Sources in Fields

A choice field can be constructed with a source or source name. When a source is used, it will be used as the source for valid values.

Create a source for all odd numbers.

>>> from zope import interface
>>> from zope.schema.interfaces import ISource, IContextSourceBinder
>>> class MySource(object):
...     interface.implements(ISource)
...     divisor = 2
...     def __contains__(self, value):
...         return bool(value % self.divisor)
>>> my_source = MySource()
>>> 1 in my_source
True
>>> 2 in my_source
False
>>> from zope.schema import Choice
>>> choice = Choice(__name__='number', source=my_source)
>>> bound = choice.bind(object())
>>> bound.vocabulary
<...MySource...>

If a IContextSourceBinder is passed as the source argument to Choice, it's bind method will be called with the context as its only argument. The result must implement ISource and will be used as the source.

>>> def my_binder(context):
...     print "Binder was called."
...     source = MySource()
...     source.divisor = context.divisor
...     return source
>>> interface.directlyProvides(my_binder, IContextSourceBinder)
>>> class Context(object):
...     divisor = 3
>>> choice = Choice(__name__='number', source=my_binder)
>>> bound = choice.bind(Context())
Binder was called.
>>> bound.vocabulary
<...MySource...>
>>> bound.vocabulary.divisor
3