How to load an instance in Django ModelForms

问题

I am using Django's user model.

How do I get a Django ModelForm to prepopulate values in a template? I know I have to use the instance for that form, but where am I going wrong below:

models.py:

class Site(models.Model):
   user = models.ForeignKey(User, )
   site_name = models.CharField(max_length=128, blank=False, null=False)

forms.py:

class SiteForm(forms.ModelForm):
      class Meta:
            model = Site
            fields = '__all__'

views.py:

def settings(request):

    site_profile = Site.objects.get(user=request.user)

    if request.method == "POST":
        form = SiteForm( instance=site_profile )
            if form.is_valid():
                form.save()

                return redirect('dashboard_home')

        else:
            form = SiteForm()

        return render(request, "dashboard/settings.html", {'form': form })

This code returns the page with no errors, however does not prepopulate the form fields with values from the database.

I can only assume the instance is not loading correctly?

回答1:

def settings(request):
    if request.method == "POST":
        form = SiteForm(request.POST, instance=request.user.site_profile)
        if form.is_valid():
            form.save()
            return redirect('dashboard_home')
    site_profile = Site.objects.get(user=request.user)
    form = SiteForm(instance=site_profile)
    return render(request, "dashboard/settings.html", {'form': form })

Your indentation was off and you never passed the site_profile to the form to have it populated. In the event of a POST request you don't want to pass the old version of site_profile to the form. I assume you want the new values the user has filled out in the template.

回答2:

In my experience, assuming the default behavior as a GET request inside function-based views will avoid some mistakes and you will get rid off those if-else statements. If you are trying to edit an object you need to populate the form during GET request too:

def settings(request):
    site_profile = Site.objects.get(user=request.user)
    form = SiteForm(instance=site_profile) # GET method
    if request.method == "POST":
        # Don't forget the request.POST !
        form = SiteForm(request.POST, instance=site_profile)
        if form.is_valid():
            form.save()
            return redirect('dashboard_home')
    return render(request, "dashboard/settings.html", {'form': form })

回答3:

def settings(request):
    site_profile = Site.objects.get(user=request.user)

    if request.method == "POST":
        form = SiteForm( instance=site_profile )
            if form.is_valid():
                form.save()

                return redirect('dashboard_home')

    else:
        form = SiteForm(instance = site_profile)

        return render(request, "dashboard/settings.html", {'form': form })

1. the else block in line 12 has one indentation to much
2. you must set the instance argument also in the else block

来源：https://stackoverflow.com/questions/31406276/how-to-load-an-instance-in-django-modelforms