On Wed, 2008-12-10 at 00:18 -0800, Tony Chu wrote: > Hi All, > > I was using the ModelForm to generate my first form in Django. > ModelForm is great. However, I had wanted to dynamically limit the > selection of Foreign keys to a subset I generate. > > The only way I found after a lot of trial and error was the following: > > form['foreignkey'].field.queryset = desiredQuerySetFromForeignKey > > Is this a good way to do it?
There's a lot of text below, but my short answer is "looks fine to me." That might, of course, be why nobody trusts my opinion, so be responsible for your own actions. > Or is there some reason why this isn't > mentioned in the documentations? Not every single possibility for setting parameters is mentioned in the documentation. Sometimes because nobody's provided documentation for it yet. Sometimes because those possibilities are sufficiently edge-case that documenting them would obscure the necessary pieces (which means documenting them really has to go into a separate section and still be findable). At some level, looking at the __init__ methods for field classes isn't that hard to do (it's pretty normal Python practice, too). Basically, documentation on various levels, given that we're catering for everybody from experienced Django users to people just learning Python and all stages in between, is an ongoing process. If you want to take a swing at writing more comprehensive documentation in this area, please do! We welcome genuine documentation improvements. As I note above, the hard bit is working out a structure so that all the necessary reference material is available (since you're really after a piece of reference documentation), without making the existing "howto" stuff less comprehensible. That's another ongoing problem we wrestle with and something that is very much ongoing work (it's easier to fix now that the docs have been restructured prior to 1.0, but it's by no means finished work). > More importantly, is there a better, more idiomatic 'Django' way to do > this? Without wanting to stamp anything as "more idiomatic", I'll say this (it's in two parts, so bear with me whilst the first bit looks like a non-solution): the reasonably standard approach if you want to change the field used by default in a ModelForm is to override that field. ForeignKeys in models are represented by ModelChoiceFields (that's documented in topcs/forms/models) which accept a queryset parameter. So you can override the field and specify whatever queryset you like. However, since you want to do this dynamically, you need to work out how to effect the same behaviour at form build time (i.e. in __init__). So the solution you've come up with is essentially the most logical: at instance creation, get the field object you're interested in and change the affected parameter. I can't see that there's anything wrong with that approach. As much as possible classes tend to be designed (not just in Django, but as a trend in Python) so that parameters can be set up by writing to attributes or calling particular methods -- that is, modified at runtime, not just at definition. Regards, Malcolm --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
