Dynamic Vocabularies in Plone Archetypes
There are certain instances where you will need a vocabulary to be dynamic in your Archetype instance. One example is if you want to display a list of objects contained in a Plone folder in a SelectionWidget.
The first thing to understand is that many archetype field attributes allow you to refer to a function, instead of a string. Until now, you've probably been using vocabularies with a DisplayList that you've defined in your config.py file:
HOUR = DisplayList((
('1', '1'),
('2', '2'),
etc....
))
StringField('hour',
vocabulary=HOUR,
widget=SelectionWidget(label='Hour',),
required=1,
),
We could just have easily defined a function to generate the HOUR DisplayList and place it in our class definition, using the DisplayList add method to build a DisplayList on the fly.
class Event(ATContent):
def getHours(self):
dl = DisplayList()
for x in range(1, 13):
dl.add(str(x))
dl.add(str(x))
return dl Now, we can call getHours from our archetypes field definition:
StringField('hour',
vocabulary="getHours",
widget=SelectionWidget(label='Hour',),
required=1,
), Now your thinking, there's got to be something more useful than creating a vocabulary of numbers from 1 to 12. What if I need to show a list of sibling objects in the same Plone folder? Let's now combine what we've just learned with Acquisition. First include this import at the top of your script:
from Acquisition import aq_parent Now, in the same way that we created getHours above, create a getLinks method to return all Link objects in the current folder:
def getLinks(self):
dl = DisplayList()
linklist = aq_parent(self).contentValues(filter={'portal_type' : 'Link'})
for link in linklist:
dl.add(link['id'], link['title'])
return dl
Then call getLinks from the vocabulary attribute:
StringField('link',
vocabulary="getLinks",
widget=SelectionWidget(label='Choose an existing link',),
required=1,
),
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