Django get_form results in unbound form (or what is the best way to get url parameters into a model-CodePudding

I'm using a model form and a CBV (createview) to build a form.

I needed to get url parameters into the form so I could access details from the previous view that sent the user to the form. To achieve this I initially tried overriding get_form as follows:

def get_form(self):
    form = AddDataForm(key_a=self.request.GET['a'], key_b=self.request.GET['b'])
    return form

This didn't work. The form wouldn't save (even when all fields were correctly completed). It would result in an unbound form.

I eventually got a positive result by using get_form_kwargs as follows:

def get_form_kwargs(self):
    kwargs = super().get_form_kwargs()
    kwargs.update({'key_a': self.request.GET['a'], 'key_b':self.request.GET['b']})

    return kwargs

My question is, what about get_form (or my lack of understanding of it) results in this behaviour?

My forms.py is below too.

class AddDataForm(forms.ModelForm):
    class Meta:
        model = MiningTech
        fields = '__all__'
        exclude = ('user',)

    def __init__(self, key_a, key_b, *args, **kwargs): # key_a comes from the view's get_form.
            super(AddDataForm, self).__init__(*args, **kwargs)
    
            if len(key_a) > 3:
                for field_name in self.fields:
                    if not field_name.startswith(key_a[0:3]): # If field_name doesn't start with first 3 characters of key_a, hide it.
                        self.fields[field_name].widget = forms.HiddenInput()
                        print("__init__ args", kwargs)
                    else:
                        self.fields[field_name].required = True                
                        self.fields['slug'].initial = key_b
                  
            else:
                print("All fields Hidden")

CodePudding user response：

The ’get_form’ is returning the instance of the form. To initiate the form, the ’get_form_kwargs’ is needed to bind your form to the instance of your model. Even if you create a new instance, the binding is needed to create the instance.

Using ’get_form_kwargs()’ is the right way to add additional argument to the form.