help with get_form_kwargs

[clavie...@gmail.com]

I have a CreateView in which I need to alter the user input. I may have found a way to do so using get_form_kwargs, but I'm puzzled by a couple of things:

I know that kwargs['data'] is a QueryDict, which is immutable. So I tried the doc's QueryDict.copy() recommendation: 

def get_form_kwargs(self):
    kwargs = super().get_form_kwargs()
    clone = kwargs['data'].copy()
    # clone = copy(kwargs['data'])
    item_num = clone['item']
    actual_item = Item.objects.get(item_number=item_num)
    clone['item'] = str(actual_item.id)
    # data.update({'item': actual_item})
    kwargs['data'] = clone
    return kwargs

It appears to work just fine until the return statement. I can step through every line and see the values change exactly the way I want them to change. By the time I get to the return statement, `clone`--which is a copy of kwargs['data']--is a QueryDict that contains the correct information. However, the program crashes with a KeyError after `kwargs` is returned, saying that kwargs['data'] doesn't exist. In the following stack trace, line 62 is the second line of the method (clone = kwargs['data'].copy()). 

KeyError at /utils/box-optimization/add-items/115

'data'

Request Method:	GET
Request URL:	http://localhost:8000/utils/box-optimization/add-items/115
Django Version:	2.0.5
Exception Type:	KeyError
Exception Value:	'data'
Exception Location:	C:\WMS Repository\Warehouse Management System\utils\views.py in get_form_kwargs, line 62
Python Executable:	C:\miniconda3\envs\django\python.exe
Python Version:	3.6.5
Python Path:	['C:\\WMS Repository\\Warehouse Management System', 'C:\\Program Files\\JetBrains\\PyCharm 2017.3.3\\helpers\\pydev', 'C:\\WMS Repository\\Warehouse Management System', 'C:\\Program Files\\JetBrains\\PyCharm 2017.3.3\\helpers\\pydev', 'C:\\Users\\heast\\.PyCharm2018.1\\system\\cythonExtensions', 'C:\\miniconda3\\envs\\django\\python36.zip', 'C:\\miniconda3\\envs\\django\\DLLs', 'C:\\miniconda3\\envs\\django\\lib', 'C:\\miniconda3\\envs\\django', 'C:\\Users\\heast\\AppData\\Roaming\\Python\\Python36\\site-packages', 'C:\\miniconda3\\envs\\django\\lib\\site-packages', 'C:\\Program Files\\JetBrains\\PyCharm ' '2017.3.3\\helpers\\pycharm_matplotlib_backend']
Server time:	Mon, 16 Jul 2018 11:16:38 -0400

Environment:

Request Method: GET

Request URL: http://localhost:8000/utils/box-optimization/add-items/115

Django Version: 2.0.5

Python Version: 3.6.5

Installed Applications:

['item.apps.ItemConfig',

 'inventory.apps.InventoryConfig',

 'fulfillment.apps.FulfillmentConfig',

 'manifest.apps.ManifestConfig',

 'order.apps.OrderConfig',

 'utils.apps.UtilsConfig',

 'django.contrib.admin',

 'django.contrib.auth',

 'django.contrib.contenttypes',

 'django.contrib.sessions',

 'django.contrib.messages',

 'django.contrib.staticfiles']

Installed Middleware:

['django.middleware.security.SecurityMiddleware',

 'django.contrib.sessions.middleware.SessionMiddleware',

 'django.middleware.common.CommonMiddleware',

 'django.middleware.csrf.CsrfViewMiddleware',

 'django.contrib.auth.middleware.AuthenticationMiddleware',

 'django.contrib.messages.middleware.MessageMiddleware',

 'django.middleware.clickjacking.XFrameOptionsMiddleware']

Traceback:

File "C:\miniconda3\envs\django\lib\site-packages\django\core\handlers\exception.py" in inner

  35.             response = get_response(request)

File "C:\miniconda3\envs\django\lib\site-packages\django\core\handlers\base.py" in _get_response

  128.                 response = self.process_exception_by_middleware(e, request)

File "C:\miniconda3\envs\django\lib\site-packages\django\core\handlers\base.py" in _get_response

  126.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "C:\miniconda3\envs\django\lib\site-packages\django\views\generic\base.py" in view

  69.             return self.dispatch(request, *args, **kwargs)

File "C:\miniconda3\envs\django\lib\site-packages\django\views\generic\base.py" in dispatch

  89.         return handler(request, *args, **kwargs)

File "C:\miniconda3\envs\django\lib\site-packages\django\views\generic\edit.py" in get

  168.         return super().get(request, *args, **kwargs)

File "C:\miniconda3\envs\django\lib\site-packages\django\views\generic\edit.py" in get

  133.         return self.render_to_response(self.get_context_data())

File "C:\WMS Repository\Warehouse Management System\utils\views.py" in get_context_data

  93.         context = super().get_context_data()

File "C:\miniconda3\envs\django\lib\site-packages\django\views\generic\edit.py" in get_context_data

  66.             kwargs['form'] = self.get_form()

File "C:\miniconda3\envs\django\lib\site-packages\django\views\generic\edit.py" in get_form

  33.         return form_class(**self.get_form_kwargs())

File "C:\WMS Repository\Warehouse Management System\utils\views.py" in get_form_kwargs

  62.         clone = kwargs['data'].copy()

Exception Type: KeyError at /utils/box-optimization/add-items/115

Exception Value: 'data'

[Matthew Pava]

I would alter user input in the clean methods.

https://docs.djangoproject.com/en/2.0/ref/forms/validation/

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[clavie...@gmail.com]

I would actually prefer to override clean(), but CreateView doesn't appear to have a clean() method that I can override. I did make a ModelForm to use with the CreateView, but the clean_item method I defined there never gets called--breakpoints and print statements are all skipped, so I don't even have any stack trace information because nothing actually breaks. I've looked through the source code and I still don't see how CreateView cleans its data. 

class AddItem(forms.ModelForm):

    class Meta:
        model = ItemsTestCollection
        fields = ['item', 'qty', 'case']

    def clean_item(self):
        print("will it print anything?")
        # Answer: nope, didn't print anything.
        item_num = self.cleaned_data['item']
        actual_item = Item.objects.get(item_number=item_num)
        return actual_item.id

I'm sure I've overlooked something simple, but meanwhile I'm looking for any kind of workaround. But thank you for the suggestion! I wish I knew how to implement it. 

To post to this group, send email to djang...@googlegroups.com.

[Matthew Pava]

This StackOverflow question may help you:

https://www.google.com/search?q=django+clean_fields+not+called&oq=django+clean_field+not+&aqs=chrome.1.69i57j0.7599j0j4&sourceid=chrome&ie=UTF-8

 

Basically this:

For any field, if the Field.clean() method raises a ValidationError, any field-specific cleaning method is not called. However, the cleaning methods for all remaining fields are still executed.

 

item should already return an instance of an Item object without your clean method. 

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[clavie...@gmail.com]

Ah, thank you for the link; it put me on the right track, I think, with custom validators. 

As an example of why I need to customize the item fetching: I have an item that has an item_number of '515874'. That number is how the users interact with the item. However, the primary key for Item '515874' is 41293, which the users don't know anything about. That way they can maintain their own internal numbering/sku system, and we don't have to worry about data integrity when they do what they need to with them. So since Django is looking for a primary key of 515874 and not finding it, it raises a ValidationError and gives up before I can get to it to tell it what the pk really is; defining my own field solved that. 

But Django is still doing something automagically, because I changed the value that it passed through my validators, returned that value, and then Django starts cleaning it... but it's trying to clean the original  '515874', not 41293, which is the value my validator returned. (I might need to start a new post simply because the topic has changed so much.) Thanks so much!

class ItemNumField(forms.CharField):

    def validate(self, value):
        # item = Item.objects.get(item_number=value)
        # value = item.id
        # return value
        return Item.objects.get(item_number=value)

class AddItem(forms.ModelForm):

    item = ItemNumField()

    class Meta:
        model = ItemsTestCollection

        # fields = ['item', 'qty', 'case']

        fields = ['item', 'qty', 'case']

class ItemsTestCollection(models.Model):
    """An item to be tested in Box Opt."""
    item = models.ForeignKey('item.Item', on_delete=models.CASCADE)
    qty = models.IntegerField()
    case = models.ForeignKey('EvaluateTestCase', on_delete=models.CASCADE)
    box = models.ForeignKey('BoxResults', on_delete=models.CASCADE, null=True)

ValueError at /utils/box-optimization/add-items/118

Cannot assign "'515874'": "ItemsTestCollection.item" must be a "Item" instance.

Request Method:	POST
Request URL:	http://localhost:8000/utils/box-optimization/add-items/118
Django Version:	2.0.5
Exception Type:	ValueError
Exception Value:	Cannot assign "'515874'": "ItemsTestCollection.item" must be a "Item" instance.
Exception Location:	C:\miniconda3\envs\django\lib\site-packages\django\db\models\fields\related_descriptors.py in __set__, line 197

Python Executable:	C:\miniconda3\envs\django\python.exe
Python Version:	3.6.5
Python Path:	['C:\\WMS Repository\\Warehouse Management System', 'C:\\Program Files\\JetBrains\\PyCharm 2017.3.3\\helpers\\pydev', 'C:\\WMS Repository\\Warehouse Management System', 'C:\\Program Files\\JetBrains\\PyCharm 2017.3.3\\helpers\\pydev', 'C:\\Users\\heast\\.PyCharm2018.1\\system\\cythonExtensions', 'C:\\miniconda3\\envs\\django\\python36.zip', 'C:\\miniconda3\\envs\\django\\DLLs', 'C:\\miniconda3\\envs\\django\\lib', 'C:\\miniconda3\\envs\\django', 'C:\\Users\\heast\\AppData\\Roaming\\Python\\Python36\\site-packages', 'C:\\miniconda3\\envs\\django\\lib\\site-packages', 'C:\\Program Files\\JetBrains\\PyCharm ' '2017.3.3\\helpers\\pycharm_matplotlib_backend']

Server time:	Mon, 16 Jul 2018 14:58:30 -0400

Environment:

Request Method: POST

Request URL: http://localhost:8000/utils/box-optimization/add-items/118

File "C:\miniconda3\envs\django\lib\site-packages\django\views\generic\edit.py" in post

  172.         return super().post(request, *args, **kwargs)

File "C:\miniconda3\envs\django\lib\site-packages\django\views\generic\edit.py" in post

  141.         if form.is_valid():

File "C:\miniconda3\envs\django\lib\site-packages\django\forms\forms.py" in is_valid

  179.         return self.is_bound and not self.errors

File "C:\miniconda3\envs\django\lib\site-packages\django\forms\forms.py" in errors

  174.             self.full_clean()

File "C:\miniconda3\envs\django\lib\site-packages\django\forms\forms.py" in full_clean

  378.         self._post_clean()

File "C:\miniconda3\envs\django\lib\site-packages\django\forms\models.py" in _post_clean

  396.             self.instance = construct_instance(self, self.instance, opts.fields, opts.exclude)

File "C:\miniconda3\envs\django\lib\site-packages\django\forms\models.py" in construct_instance

  60.             f.save_form_data(instance, cleaned_data[f.name])

File "C:\miniconda3\envs\django\lib\site-packages\django\db\models\fields\__init__.py" in save_form_data

  838.         setattr(instance, self.name, data)

File "C:\miniconda3\envs\django\lib\site-packages\django\db\models\fields\related_descriptors.py" in __set__

  197.                     self.field.remote_field.model._meta.object_name,

Exception Type: ValueError at /utils/box-optimization/add-items/118

Exception Value: Cannot assign "'515874'": "ItemsTestCollection.item" must be a "Item" instance.