Ok! I think I see your problem.
It is a deeper understanding of python classes that may be the problem.
You see, "model" and "self" are class atributes of the python class that
houses your class based view (as every class in django is first a python
class).
So, if you try to access the attribute "model" of the class, or the
attribute "self", a attribute that houses the instance of the class, on
it's class attributes definitions you will have problems, as the python
interpreter only load these modules lazyly, not actually going through on
finding the value for the attribute you referenced.
One solution is to have that value (for the attribute "field" as a
@property that is a function that then the python interpreter will go
through and execute the reference lookup.
Another solution is to set that value to be initially None, and set the
value for the fields on the dispatch method of the view, something like
class ItemUpdateView(UpdateView):
template_name="foo.html"
fields = None
def dispatch (self, request, *args, **kwargs):
self.fields = self.model.fields
return super(ItemUpdateView, self).dispatch(request, *args, **kwargs)
But as of my understanding of your problem, you are trying to just
customize which form fields to display to the user based on which model the
user is updating, so you could just specify the form_class attribute on the
path (just as you did with the model).
Hope it helps!
On Wed, Jun 6, 2018, 10:36 Mikkel Kromann <[email protected]> wrote:
> Hello Daniel.
>
> Thank you for your reply. Perhaps I was not explicit enough in describing
> my problem - it is far simpler than your solution indicates.
> In my model definitions, I already have a list of the fields to be
> represented in the form of UpdateView - it is an attribute in the form of a
> simple array called "fields".
> I don't want UpdateView to make a form for all columns of the model's data
> table, just the fields from my custom array in the Model objects.
>
> My problem is simply: How to access my custom attribute "field" in the
> Model attribute passed to the Class Based View function.
> As described, I get compilation errors, complaining that "model" and
> "self" are names not defined.
> From the documentation (and my so far not too great Python understandign)
> it is not clear to me whether "Model" is simply the name of the model, or
> if it is the entire Model object instance.
>
>
> thanks again, Mikkel
>
>
> onsdag den 6. juni 2018 kl. 15.01.05 UTC+2 skrev Daniel Germano Travieso:
>>
>> Hello!
>>
>> As you see on the documentation (
>> https://docs.djangoproject.com/en/2.0/topics/class-based-views/) for the
>> class based views, any arguments you pass to the class based view
>> .as_view() method will override attributes of the class based view, so if
>> you set MyCView.as_view(model=Foo) is the same as setting class MyCView:
>> model=Foo directly.
>>
>> Now to access the field names of the Model, you used to be able to call a
>> .get_field_names() or something like that but that is depreciated since
>> 1.10. Now to do that you should use the Model._meta to get_fields(). Check
>> the documentation for the Model._meta to check its full potential.
>>
>> Hope it helps!
>>
>> On Wed, Jun 6, 2018, 07:33 Mikkel Kromann <[email protected]>
>> wrote:
>>
>>> Thanks for the advice, Andréas.
>>> But the response is the same:
>>>
>>> File "C:\Users\ ... xxxxxxx ... \items\views.py", line 7, in
>>> ItemUpdateView
>>> fields = self.model.fields
>>> NameError: name 'self' is not defined
>>>
>>>
>>>
>>> As far as I understood, model is an attribute, not a method (though I'm
>>> new to Python and Django, so I'm unsure about this).
>>> Does attribute/method make a difference in this case?
>>>
>>> cheers, Mikkel
>>> tirsdag den 5. juni 2018 kl. 22.10.31 UTC+2 skrev Andréas Kühne:
>>>>
>>>> Hi,
>>>>
>>>> Have you tried self.model? It should be present in all methods in the
>>>> class?
>>>>
>>>> Regards,
>>>>
>>>> Andréas
>>>>
>>>> 2018-06-05 21:56 GMT+02:00 Mikkel Kromann <[email protected]>:
>>>>
>>>>> Dear Django-users.
>>>>>
>>>>> I'm slowly working towards a Django "data-warehouse" framework, where
>>>>> I can easily add a lot of models (each containing a table with data),
>>>>> while
>>>>> sticking to only few reusable views.
>>>>>
>>>>> I've realised that in urls.py, it is possible to specify the model on
>>>>> which the UpdateView is going to do its magic.
>>>>> This allows me to use a generic UpdateView (which I called
>>>>> ItemUpdateView) and template for all my models, which will save me a ton
>>>>> of
>>>>> almost identical lines of code.
>>>>>
>>>>> However, in the generic ItemUpdateView, I of course need to specify
>>>>> the fields of the specific model chosen in urls.py.
>>>>> As I ideally only want a few generic views (i.e. ItemCreateView,
>>>>> ItemUpdateView, ItemDeleteView and ItemListView), I've chosen to place the
>>>>> field array in my model definition, hoping to be able to access it from my
>>>>> generic Class Based Views
>>>>>
>>>>> But how do I access the model attribute in (Item)UpdateView
>>>>>
>>>>>
>>>>> thanks, Mikkel
>>>>>
>>>>> From views.py
>>>>> from django.views.generic import CreateView, ListView, UpdateView,
>>>>> DeleteView
>>>>>
>>>>> class ItemUpdateView(UpdateView):
>>>>> template_name = "item_form.html"
>>>>> # How do I access the model attribute of ItemUpdateView as given in
>>>>> urls.py?
>>>>> # This line below returns the error "NameError: name 'model' not
>>>>> defined"
>>>>> fields = model.fields
>>>>>
>>>>> From urls.py
>>>>> from django.urls import path
>>>>> from . views import ItemUpdate
>>>>> from . models import Region, Location
>>>>>
>>>>> # Awesome! I can specify the model to be used by ItemUpdateView
>>>>> urlpatterns = [
>>>>> path('update/region/<pk>', ItemUpdateView.as_view(model=Region
>>>>> ), name='region_update'),
>>>>> path('update/location/<pk>', ItemUpdateView.as_view(model=
>>>>> Location), name='location_update'),
>>>>> ]
>>>>>
>>>>>
>>>>>
>>>>> From models.py (Region and Location are only two of my tables, I'd
>>>>> like to have say 20 or 30 models
>>>>> from django.db import models
>>>>>
>>>>> # Abstract class for our items including common methods, data and
>>>>> definitions
>>>>> class ItemModel(models.Model):
>>>>>
>>>>> fields = [ 'label', 'short', 'descr' ]
>>>>> label = models.CharField(max_length=10)
>>>>> short = models.CharField(max_length=15)
>>>>> descr = models.CharField(max_length=40)
>>>>>
>>>>> def __str__(self):
>>>>> return self.short
>>>>>
>>>>> class Meta:
>>>>> abstract = True
>>>>>
>>>>> class Region(ItemModel):
>>>>> fields = [ 'label', 'short', 'descr' ]
>>>>>
>>>>> class Location(ItemModel):
>>>>> fields = [ 'label', 'short', 'descr', 'region' ]
>>>>> region = models.ForeignKey(Region, on_delete=models.CASCADE)
>>>>>
>>>>> class Plant(ItemModel):
>>>>> fields = [ 'label', 'short', 'descr', 'location', 'capex',
>>>>> 'opex', 'capacity' ]
>>>>> location= models.ForeignKey(Location, on_delete=models.CASCADE)
>>>>> capex = models.DecimalField(decimal_places=3, max_digits=8)
>>>>> opex = models.DecimalField(decimal_places=3, max_digits=8)
>>>>> capacity= models.DecimalField(decimal_places=3, max_digits=8)
>>>>>
>>>>>
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