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Forms meta-package for Dolmen, using megrok.z3cform.base and z3c.form

Project description

dolmen.forms.base is a package in charge of exposing all the functionalities of z3c.form and megrok.z3cform, to allow an easy import. This package, developed for the Dolmen project, makes it easier to change the underlying form framework. In the long run, z3c.form and megrok.z3cform might be replaced by zeam.form.

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.


0.1 - Unreleased

  • Initial release

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