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Spotlight on: dolmen.content

The package `dolmen.content` is a convenient way to define content types. Written by Souheil CHELFOUH.

This spotlight is about dolmen.content, which is the first package I wrote for Grok and the Dolmen project. It first was a Plone package, using five, and five.grok, and it was called "spear.content" (in 2007). I refactored it partially, while I stopped Ploning and first started the Dolmen project (ex-spear) It's used outside of the Dolmen project in another Grok project called uvcsite, coded by Christian Klinger.

dolmen.content

The package dolmen.content is a convenient way to define content types. Content types usually have several attributes : a type, a schema, an icon. In addition, they need security to control the creation, pages to edit them, easy ways to control the display, and the widgets. This is what provides dolmen.content, with an easy-to-use set of grok directives.

Example

A dolmen.content content is declared as a simple class. Some directives are available to define your content: name, icon, schema and factory. To have detailed information about these directives, please have a look at the package tests.

Defining the content

Let's demonstrate the package's features with a simple and non-exhaustive test:

>>> import dolmen.content
>>> from zope import schema

>>> class IContentSchema(dolmen.content.IBaseContent):
...    text = schema.Text(title=u"A body text", default=u"N/A")

>>> class MyContent(dolmen.content.Content):
...  """A very simple content
...  """
...  dolmen.content.schema(IContentSchema)
...  dolmen.content.name("a simple content type")
Schema

The content can now be instanciated. As we can see here, the object is effectively providing the schema, even without grokking:

>>> MyContent.text
<zope.schema.fieldproperty.FieldProperty object at ...>

>>> IContentSchema.implementedBy(MyContent)
True

>>> obj = MyContent()
>>> obj.text
u'N/A'
Grokking

We now let Grok register our component:

>>> from grokcore.component import testing
>>> testing.grok_component('mycontent', MyContent)
True
Factory

When the content is registered, a factory is registered, using the full module and class dotted names. It allows us to query and instanciate the content easily:

>>> from zope.component import getUtility
>>> factory = getUtility(dolmen.content.IFactory,
...                      name="dolmen.content.MyContent")
>>> factory
<dolmen.content.factoring.Factory object at ...>

Foot notes for the grokkers out there

If you thought that Spotlight was too much code, or not detailed enough, please let me know I'll try to cover most of the interesting packages I released lately. Please note, also, that dolmen.content is currenty under heavy surgery. At the moment, the schema fields boostrap is done by a grokker. I decided to drop this and use a zope.interface ClassAdvisor, to allow very straightforward bootstrapping, even on non grokked objects. Also, the 'icon' directive should disapear, soon, if I can get a decent release of megrok.icon (another package I need to work on !)