How do I add a Foreign Key Field to a ModelForm in Django?

What I would like to do is to display a single form that lets the user:

• Enter a document title (from Document model)
• Select one of their user_defined_code choices from a drop down list (populated by the UserDefinedCode model)
• Type in a unique_code (stored in the Code model)

I'm not sure how to go about displaying the fields for the foreign key relationships in a form. I know in a view you can use document.code_set (for example) to access the related objects for the current document object, but I'm not sure how to apply this to a ModelForm.

My model:

class UserDefinedCode(models.Model): name = models.CharField(max_length=8) owner = models.ForeignKey(User) class Code(models.Model): user_defined_code = models.ForeignKey(UserDefinedCode) unique_code = models.CharField(max_length=15) class Document(models.Model): title = models.CharField(blank=True, null=True, max_length=200) code = models.ForeignKey(Code) active = models.BooleanField(default=True)

My ModelForm

class DocumentForm(ModelForm): class Meta: model = Document

django  django-models  django-forms  foreign-keys

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asked  Apr 18 '11 at 20:42

Ben S

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1 Answer

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In regards to displaying a foreign key field in a form you can use the forms.ModelChoiceField and pass it a queryset.

so, forms.py:

class DocumentForm(forms.ModelForm): class Meta: model = Document def __init__(self, *args, **kwargs): user = kwargs.pop('user','') super(DocumentForm, self).__init__(*args, **kwargs) self.fields['user_defined_code']=forms.ModelChoiceField(queryset=UserDefinedCode.objects.filter(owner=user))

views.py:

def someview(request): if request.method=='post': form=DocumentForm(request.POST, user=request.user) if form.is_valid(): selected_user_defined_code = form.cleaned_data.get('user_defined_code') #do stuff here else: form=DocumentForm(user=request.user) context = { 'form':form, } return render_to_response('sometemplate.html', context, context_instance=RequestContext(request))

from your question:

I know in a view you can use document.code_set (for example) to access the related objects for the current document object, but I'm not sure how to apply this to a ModelForm.

Actually, your Document objects wouldn't have a .code_set since the FK relationship is defined in your documents model. It is defining a many to one relationship to Code, which means there can be many Document objects per Code object, not the other way around. Your Code objects would have a .document_set. What you can do from the document object is access which Code it is related to using document.code.

edit: I think this will do what you are looking for. (untested)

forms.py:

class DocumentForm(forms.ModelForm): class Meta: model = Document exclude = ('code',) def __init__(self, *args, **kwargs): user = kwargs.pop('user','') super(DocumentForm, self).__init__(*args, **kwargs) self.fields['user_defined_code']=forms.ModelChoiceField(queryset=UserDefinedCode.objects.filter(owner=user)) self.fields['unique_code']=forms.CharField(max_length=15)

views.py:

def someview(request): if request.method=='post': form=DocumentForm(request.POST, user=request.user) if form.is_valid(): uniquecode = form.cleaned_data.get('unique_code') user_defined_code = form.cleaned_data.get('user_defined_code') doc_code = Code(user_defined_code=user_defined_code, code=uniquecode) doc_code.save() doc = form.save(commit=False) doc.code = doc_code doc.save() return HttpResponse('success') else: form=DocumentForm(user=request.user) context = { 'form':form, } return render_to_response('sometemplate.html', context, context_instance=RequestContext(request))

actually you probably want to use get_or_create when creating your Code object instead of this.

doc_code = Code(user_defined_code=user_defined_code, code=uniquecode)