dolmen.forms.base 0.1

Field update

dolmen.forms.base also proposes the definition of a new component that can be used to atomize the updating process of an object: IFieldUpdate.

To demonstrate this IFieldUpdate, we are going to implement a simple usecase where we instanciate a content, change a value and notify the IFieldUpdate components. For that, we’ll use a basic logger object:

>>> logger = []

We create our test model:

>>> from zope.schema import TextLine
>>> from zope.interface import Interface, implements

>>> class IContent(Interface):
...    title = TextLine(title=u'a title')

>>> class Item(object):
...    implements(IContent)

Once this is done, we can define two IFieldUpdate components. We implement them as named adapters. We’ll retrieve them thanks to a “getAdapters” call:

>>> from zope.component import adapter
>>> from zope.interface import implementer
>>> from dolmen.forms.base import IFieldUpdate

>>> @implementer(IFieldUpdate)
... @adapter(TextLine, IContent)
... def updated_title(field, context):
...    if field.__name__ == u"title":
...       logger.append('Title updated on %r with `%s`' %
...                     (context, getattr(context, field.__name__)))

>>> @implementer(IFieldUpdate)
... @adapter(TextLine, Interface)
... def updated_textfield(field, context):
...    logger.append('A text field has been updated')

The components need to be named since they are adapters: we don’t want them to override each other. For the example, we want them both. let’s register them:

>>> from zope.component import provideAdapter
>>> provideAdapter(updated_title, name="updatetitle")
>>> provideAdapter(updated_textfield, name="updatetext")

Now, we develop the small scenarii : we instanciate a Content, add a value for the ‘title’ attribute and call the adapters:

>>> item = Item()
>>> item.title = "Some value"

>>> from zope.component import getAdapters
>>> adapters = getAdapters((IContent['title'], item), IFieldUpdate)
>>> for adapter in adapters:
...   # We run through the generator
...   pass

>>> for line in logger: print line
Title updated on <Item object at ...> with `Some value`
A text field has been updated

It works.

Changelog

0.1 - Unreleased

• Initial release