change modelform values after POST

[Cesar Devera]

hi.

I have a ModelForm based on an Model like this:

class MyModel(models.Model):
attr1 = models.CharField()
attr2 = models.CharField()
attr3 = models.CharField()
createdby = models.ForeignKey(User, related_name='createdby',
db_column='createdbyid')
calculatedfield = models.CharField()

class MyModelForm(ModelForm):
class Meta:
model = MyModel

the attribute fields attr1, attr2 and attr3 are properly shown on my
html page, and correctly restored on my server-side view like this:

def save(request,id):
user = request.user
try:
mymodel = MyModel.objects.get(pk=id)
except:
mymodel = MyModel()
form = MyModelForm(request.POST, instance=mymodel)

now comes the problem: I want to set the createdby attribute only on
my view, AFTER the html page Post. I want to set the createdby and any
other calculated field on server side. is it possible?

I tried:

form['createdby'] = request.user

but it didn't seem to work.

this field (createdby) is NOT NULL and so I wouldn't like to set it to
NULL, save the form with form.save() and later recover the entity
again and manipulate the remaining fields...

any ideas?

thanks in advance.

[Bjunix]

You probably want to change the attributes of the model object
directly.

"If you call save() with commit=False, then it will return an object
that hasn't yet been saved to the database."
Source: http://docs.djangoproject.com/en/dev/topics/forms/modelforms/#the-save-method

So I would do something like this:

def my_change_view(request, id):
#get instance based on id here
#....
if request.method == 'POST':
form = MyModelForm(request.POST, instance=instance)
if form.is_valid():
obj = form.save(commit=False)
obj.created_by = request.user
obj.save()
form.save_m2m()
return redirect('/somewhere')
else:
form = MyModelForm(instance=instance)
return render_to_response.....

I hope this helps. Remember to call form.save_m2m() if your model has
any many-to-many relations. I also would suggest to (re-)read django's
excellent documentation forms.

[tc]

On 21 mar, 22:38, Bjunix <bju...@bjunix.de> wrote:
> You probably want to change the attributes of the model object
> directly.
>
> "If you call save() with commit=False, then it will return an object
> that hasn't yet been saved to the database."

> Source:http://docs.djangoproject.com/en/dev/topics/forms/modelforms/#the-sav...

>
> So I would do something like this:
>
> def my_change_view(request, id):
>     #get instance based on id here
>     #....
>     if request.method == 'POST':
>         form = MyModelForm(request.POST, instance=instance)
>             if form.is_valid():
>                 obj = form.save(commit=False)
>                 obj.created_by = request.user
>                 obj.save()
>                 form.save_m2m()
>                 return redirect('/somewhere')
>     else:
>         form = MyModelForm(instance=instance)
>     return render_to_response.....
>
> I hope this helps. Remember to call form.save_m2m() if your model has
> any many-to-many relations. I also would suggest to (re-)read django's
> excellent documentation forms.
>

I see that the problem I have had today is exactly the same. The only
problem of the solution you are
proposing here is that created_by could not be mandatory. If it is,
the form would be not valid.

[Paulo Almeida]

It depends on what you want. You can set 'created_by' to blank=True and null=False, so it doesn't have to be filled but it is still mandatory in the database. Or, if you never want to set it in the form, you can make it 'editable=False' and it doesn't show up in the form, but it can still be NOT NULL. Of course, you must make sure it is filled in some way.

- Paulo

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