Not much more than a noob myself - I hope the following will be
useful:
1. form_from_model (and form_from_instance) are merely shortcuts -
allowing you to build a form that has all the fields from the target
model. In most real-life cases, you only need some of the fields, and
as mentioned you are probably getting user input for more than just
one model at a time. So you can go with the basic newforms approach of
defining your form class *as per how you want the HTML form to look
like*, and map back into instance data in your view function that
handled the post data. After checking that the form is valid you
simply instantiate what you need from your models and assign values
from the relevant form fields into the instances you have created.
Then you save() them.
Obviously this means you have manual code that copies data from the
form fields to the instance fields, and that will need to be
maintained in parallel to the changes in the model. But as in many
cases the HTML forms are pretty far from being a 1-to-1 representation
of the models (admin interface is the exception), the form-for-model
shortcut is probably not what you need anyway.
2. For M2M data, which is not saved by the form_for_model shortcut on
save(), you can still use the form_for_model shortcut but you will
need to iterate over the M2M field's (form field) data, and call the
relevant *add() method (I'm assuming you're only adding refs to
existing M2M target instances). For instance if you have:
class Client(model):
name = CharField(...)
tags = M2MField(Tag,...)
...
class Tag(model):
name = CharField(...)
...
then a paraphrase of your original code snippet would go like:
if client_form.is_valid():
client = client_form.save(commit=False)
client.institution =
Institution.objects.get(pk=site_id)
# repeat this for any m2m field
client.tags.add(*client_form.clean_data['tags']) # add
accepts a variable number of args - note use of '*'
client.save()
return HttpResponseRedirect('/myapp/client/%s' %
(client.id))
On Jun 5, 4:52 pm, larry <[EMAIL PROTECTED]> wrote:
> > I'm not sure what "a patch in the development tree" means here. Current
> > subversion trunk doesn't seem to have anything like that.
>
> Sorry for not being clear -- I'm (obviously) not familiar with the
> mechanism of open source / django development. What I was referring
> to is the ticket you mentioned (4001) and the "patch" is the file
> attached to that ticket (save_instance_m2m.patch).
>
> > Remember that the situation where a form maps precisely onto a model is
> > a very specialised case. In the general case, you need to build the
> > objects you are going to save manually anyway (since one form provides
> > information for many models). So the workaround that springs to mind in
> > this case is to forget about using form_for_model() and just build the
> > form by hand and construct the save objects in your view. It's only a
> > few lines of code.
>
> That sounds great (in fact, I was forced to combine two tables into
> one in order to coerce the data into something that can be easily used
> by form_for_model). However, I'm not sure where to start to come to
> grips with the concepts of "objects you are going to save", "build the
> form by hand", and "construct the save objects".
>
> I'm guessing that this means instantiating models, creating the form
> bound to data from several different model classes, then (on POST)
> instantiating new model instances, somehow unpacking the data from the
> form into the appropriate model classes, and saving the instances.
>
> If you can direct me to a simple example of a view that does this
> (including a many-to-many field in one of the models if such a field
> requires any special handling in the view) it would be greatly
> appreciated. I guess my three sticking points are 1) how to create a
> form from _several_ objects, 2) how to create the form from several
> _models_ when the user is trying to add new information and 3) how to
> instantiate the multiple save objects from the POSTed form.
>
> Many thanks for your kind assistance in what I know must be quite a
> simple operation.
> --
> Larry Lustig
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