Newforms has a spiffy way to dynamically set the "initial" values of
fields, in the view code when the Form is constructed.
choosecolorform = ChooseColorForm(initial={'color': 'black'})
I was hoping it would be just as easy to dynamically define the
choices available in a ChoiceField, too... but no such luck.
The choices in my ChoiceField will ultimately come from a database,
and will vary based on user permissions and/or the state of the page
that the form is being displayed on, etc. For a contrived example,
consider paint-color choices that will depend on whether the form is
on a page displaying a metal object that takes enamel, or a wooden
object that takes latex paint.
I'd rather not make my Form be "aware" of my database, or the page
it's on, because that seems like poor encapsulation and probably a
violation of the DRY principle (I'm just going on intuition here,
though).
So here's what I'm doing, to allow my view to dynamically tweak the
choices:
////////myforms.py:
from django import newforms as forms
class ChooseColorForm(forms.Form):
color = forms.ChoiceField(initial="unpainted", choices =
[("unpainted", "Don't paint it"),], label="Choose a color")
def setchoices(self, choices):
field = None
for item in self.fields.items():
if item[0]=="color":
field = item[1]
if field:
field.choices = choices
field.initial = choices[0][0]
else:
print "INTERNAL ERROR! No color field found on ChooseColorForm
object"
# /class ChooseColorForm
////////views.py:
from myforms import ChooseColorForm
def remodelthingypage(httpreq):
# ...
choosecolorform = ChooseColorForm()
if thingy.ismetal:
choosecolorform.setchoices(_getenamelpaintcolors(sa))
else:
choosecolorform.setchoices(_getlatexpaintcolors(sa))
return _respond(httpreq, 'remodeling.html', { 'thingy': thingy,
'choosecolorform': choosecolorform, })
# /remodelthingypage()
* NOTE: For my contrived example, I could obviously just make two Form
subclasses, one for latex paints and another for enamels, but the
actual scenario is more complicated and there are other factors
involved in determining the available choices, such as whether there's
enough of that color in stock to cover the whole thingy or not.
So anyway, this technique WORKS -- but I'm a bit tentative about it
because:
a) I'm still a Django *AND* a Python novice, and
b) I had to dig around in the newforms code to figure out how to ram
my own choices into the form object, which is dangerous because
there's no private/protected to warn me not to screw around with that,
AND my code is now tied to the internal implementation of newforms.
Afterwards, I found a blog entry that does something similar,
http://www.zoia.org/blog/2007/04/23/using-dynamic-choices-with-django-newforms-and-custom-widgets/
but it uses:
Form.base_fields['tags'].choices
rather than my:
Form.fields.items()[x][1].choices
That makes my goofy for-loop unnecessary, but I'm not sure what the
implications of each are (too lazy to analyze all the newforms code,
plus I wanted to ask anyway, because I don't know what the plans/
vision for newforms is)
So, are there better techniques for dynamically setting the choices in
a newforms ChoiceField? (Or, is my whole approach dumb.?)
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Django users" group.
To post to this group, send email to django-users@googlegroups.com
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/django-users?hl=en
-~----------~----~----~----~------~----~------~--~---
