Re: dynamic forms and custom methods

[Nick]

I think jquery may be the right way to go for this. It will allow you
to evaluate the weights in real time so you won't have to submit the
form before any validation errors would be returned.

Working it at the model level may get tricky, for ease I would handle
it at the form or view level.

On Aug 12, 9:30 am, Steve Holden  wrote:
> On 8/12/2010 8:36 AM, lingrlongr wrote:
>
>
>
> > Hi Nick,
>
> > Thanks for the reply.  Yes, the department weights will be used in a
> > grading scheme.  One department may be 25% (0.25), etc...  But in the
> > end, the weights should total 1.0.  For example, in my Store model:
>
> > class Store(models.Model):
> >   #...etc...
>
> >   def _get_total_dept_weight(self):
> >     return self.department_set.all().aggregate(Sum('weight'))
> > ['weight_sum']
>
> >   def save(self, *args, **kwargs):
> >     if self._get_total_dept_weight() <> Decimal('1.0'):
> >       # fail
> >     super(Store, self).save(*args, **kwargs)
>
> > So in the case of my custom form, I was thinking about raising a
> > validation error if the totals submitted in the form don't total 1.0.
> > But I was thinking over the weekend, maybe this isn't the best place
> > for it after all. Maybe it should stay in the model because why does
> > the form care if the weights is 1.0?  The model does...  Perhaps
> > instead, raise a ValidationError exception from the Store's save()
> > method?
>
> Yes, you could do that - and even if you used JavaScript on the client
> side to enforce the total it would still be necessary to avoid malicious
> clients.
>
> > What are your thoughts?
>
> Alternatively, you could just normalize the weights after the user
> submits them, or even leave them as they are and normalize them when you
> use them. Surely the important thing is the weightings and their
> relative values. You can simply divide each weighting by the sum of all
> weightings before you apply them.
>
> regards
>  Steve
>
>
>
>
>
> > On Aug 11, 3:58 pm, Nick  wrote:
> >> Are you trying to create a save function that evaluates all the
> >> weights and returns an error if they are more than 1?
>
> >> On Aug 10, 3:17 pm, lingrlongr  wrote:
>
> >>> I 'm trying to create a form dynamically.  This works just fine, but
> >>> there's no way for the form to offer any customized validation, by way
> >>> of the clean() method.
>
> >>> def get_dept_weight_form(store):
> >>>     fields = {}
> >>>     s = Store.objects.get(pk=store.id)
> >>>     for d in store.department_set.all():
> >>>         fields['id_%d' % d.id] = forms.DecimalField(
> >>>             label = d.name,
> >>>             initial = d.weight
> >>>         )
> >>>     return type('WeightForm', (forms.BaseForm,), {'base_fields':
> >>> fields})
>
> >>> Basically, this form spits out a label showing the department name and
> >>> the weight for you to enter in a textbox.  The weights for all
> >>> departments should total 1.0.  Should a clean() method handle this?
>
> >>> I already use an overridden version of save() on the store model, but
> >>> that just prints out a warning to stdout.  Also, I have this
> >>> validation for the admin part by overriding the clean method for my
> >>> declared ModelForm.
>
> >>> Perhaps I should just use the functionality I already created in
> >>> models.py and just raise a ValidationError?
>
> >>> Thx
>
> --
> DjangoCon US 2010 September 7-9http://djangocon.us/

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Re: dynamic forms and custom methods

[Steve Holden]

On 8/12/2010 8:36 AM, lingrlongr wrote:
> Hi Nick,
> 
> Thanks for the reply.  Yes, the department weights will be used in a
> grading scheme.  One department may be 25% (0.25), etc...  But in the
> end, the weights should total 1.0.  For example, in my Store model:
> 
> class Store(models.Model):
>   #...etc...
> 
>   def _get_total_dept_weight(self):
> return self.department_set.all().aggregate(Sum('weight'))
> ['weight_sum']
> 
>   def save(self, *args, **kwargs):
> if self._get_total_dept_weight() <> Decimal('1.0'):
>   # fail
> super(Store, self).save(*args, **kwargs)
> 
> So in the case of my custom form, I was thinking about raising a
> validation error if the totals submitted in the form don't total 1.0.
> But I was thinking over the weekend, maybe this isn't the best place
> for it after all. Maybe it should stay in the model because why does
> the form care if the weights is 1.0?  The model does...  Perhaps
> instead, raise a ValidationError exception from the Store's save()
> method?
> 
Yes, you could do that - and even if you used JavaScript on the client
side to enforce the total it would still be necessary to avoid malicious
clients.

> What are your thoughts?
> 
Alternatively, you could just normalize the weights after the user
submits them, or even leave them as they are and normalize them when you
use them. Surely the important thing is the weightings and their
relative values. You can simply divide each weighting by the sum of all
weightings before you apply them.

regards
 Steve

> On Aug 11, 3:58 pm, Nick  wrote:
>> Are you trying to create a save function that evaluates all the
>> weights and returns an error if they are more than 1?
>>
>> On Aug 10, 3:17 pm, lingrlongr  wrote:
>>
>>> I 'm trying to create a form dynamically.  This works just fine, but
>>> there's no way for the form to offer any customized validation, by way
>>> of the clean() method.
>>
>>> def get_dept_weight_form(store):
>>> fields = {}
>>> s = Store.objects.get(pk=store.id)
>>> for d in store.department_set.all():
>>> fields['id_%d' % d.id] = forms.DecimalField(
>>> label = d.name,
>>> initial = d.weight
>>> )
>>> return type('WeightForm', (forms.BaseForm,), {'base_fields':
>>> fields})
>>
>>> Basically, this form spits out a label showing the department name and
>>> the weight for you to enter in a textbox.  The weights for all
>>> departments should total 1.0.  Should a clean() method handle this?
>>
>>> I already use an overridden version of save() on the store model, but
>>> that just prints out a warning to stdout.  Also, I have this
>>> validation for the admin part by overriding the clean method for my
>>> declared ModelForm.
>>
>>> Perhaps I should just use the functionality I already created in
>>> models.py and just raise a ValidationError?
>>
>>> Thx
>>
>>
> 


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Re: dynamic forms and custom methods

[lingrlongr]

Hi Nick,

Thanks for the reply.  Yes, the department weights will be used in a
grading scheme.  One department may be 25% (0.25), etc...  But in the
end, the weights should total 1.0.  For example, in my Store model:

class Store(models.Model):
  #...etc...

  def _get_total_dept_weight(self):
return self.department_set.all().aggregate(Sum('weight'))
['weight_sum']

  def save(self, *args, **kwargs):
if self._get_total_dept_weight() <> Decimal('1.0'):
  # fail
super(Store, self).save(*args, **kwargs)

So in the case of my custom form, I was thinking about raising a
validation error if the totals submitted in the form don't total 1.0.
But I was thinking over the weekend, maybe this isn't the best place
for it after all. Maybe it should stay in the model because why does
the form care if the weights is 1.0?  The model does...  Perhaps
instead, raise a ValidationError exception from the Store's save()
method?

What are your thoughts?

On Aug 11, 3:58 pm, Nick  wrote:
> Are you trying to create a save function that evaluates all the
> weights and returns an error if they are more than 1?
>
> On Aug 10, 3:17 pm, lingrlongr  wrote:
>
> > I 'm trying to create a form dynamically.  This works just fine, but
> > there's no way for the form to offer any customized validation, by way
> > of the clean() method.
>
> > def get_dept_weight_form(store):
> >     fields = {}
> >     s = Store.objects.get(pk=store.id)
> >     for d in store.department_set.all():
> >         fields['id_%d' % d.id] = forms.DecimalField(
> >             label = d.name,
> >             initial = d.weight
> >         )
> >     return type('WeightForm', (forms.BaseForm,), {'base_fields':
> > fields})
>
> > Basically, this form spits out a label showing the department name and
> > the weight for you to enter in a textbox.  The weights for all
> > departments should total 1.0.  Should a clean() method handle this?
>
> > I already use an overridden version of save() on the store model, but
> > that just prints out a warning to stdout.  Also, I have this
> > validation for the admin part by overriding the clean method for my
> > declared ModelForm.
>
> > Perhaps I should just use the functionality I already created in
> > models.py and just raise a ValidationError?
>
> > Thx
>
>

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Re: dynamic forms and custom methods

[Nick]

Are you trying to create a save function that evaluates all the
weights and returns an error if they are more than 1?

On Aug 10, 3:17 pm, lingrlongr  wrote:
> I 'm trying to create a form dynamically.  This works just fine, but
> there's no way for the form to offer any customized validation, by way
> of the clean() method.
>
> def get_dept_weight_form(store):
>     fields = {}
>     s = Store.objects.get(pk=store.id)
>     for d in store.department_set.all():
>         fields['id_%d' % d.id] = forms.DecimalField(
>             label = d.name,
>             initial = d.weight
>         )
>     return type('WeightForm', (forms.BaseForm,), {'base_fields':
> fields})
>
> Basically, this form spits out a label showing the department name and
> the weight for you to enter in a textbox.  The weights for all
> departments should total 1.0.  Should a clean() method handle this?
>
> I already use an overridden version of save() on the store model, but
> that just prints out a warning to stdout.  Also, I have this
> validation for the admin part by overriding the clean method for my
> declared ModelForm.
>
> Perhaps I should just use the functionality I already created in
> models.py and just raise a ValidationError?
>
> Thx

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dynamic forms and custom methods

[lingrlongr]

I 'm trying to create a form dynamically.  This works just fine, but
there's no way for the form to offer any customized validation, by way
of the clean() method.

def get_dept_weight_form(store):
fields = {}
s = Store.objects.get(pk=store.id)
for d in store.department_set.all():
fields['id_%d' % d.id] = forms.DecimalField(
label = d.name,
initial = d.weight
)
return type('WeightForm', (forms.BaseForm,), {'base_fields':
fields})

Basically, this form spits out a label showing the department name and
the weight for you to enter in a textbox.  The weights for all
departments should total 1.0.  Should a clean() method handle this?

I already use an overridden version of save() on the store model, but
that just prints out a warning to stdout.  Also, I have this
validation for the admin part by overriding the clean method for my
declared ModelForm.

Perhaps I should just use the functionality I already created in
models.py and just raise a ValidationError?

Thx

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