Django-表单字段的值作为另一个表单字段的默认值

Question

我想填写我的表单域（URL），并在下一个表单域（在另一个视图中）使用该URL作为默认值。 我无法切换视图并采用该表单值。 有什么建议吗？ 这是我的文件：

views.py

def subcategory(request, category_name_slug, subcategory_name_slug):
    context = {}
    form = SiteAddForm()
    context['form'] = form
    try:
        category = Category.objects.get(slug=category_name_slug)
        subcategory = SubCategory.objects.filter(category=category
                                             ).get(slug=subcategory_name_slug)
        sites = Site.objects.filter(subcategory=subcategory)
        context['subcategory'] = subcategory
        context['sites'] = sites
    except (SubCategory.DoesNotExist, Category.DoesNotExist):
        raise Http404("Nie ma takiej strony")
    if request.method == 'POST':
        form = SiteAddForm(request.POST)
        if form.is_valid():
            siteurl = form.cleaned_data['url']
            context['siteurl'] = siteurl
            return render(request, 'mainapp/add_site.html', context)
return render(request, 'mainapp/subcategory.html', context)

def add_site(request, category_name_slug, subcategory_name_slug):
context = {}
forms = SiteAddFormA()
context['form'] = forms

return render(request, 'mainapp/add_site.html', context)

forms.py：

from django import forms
from mainapp.models import Site


class SiteAddForm(forms.Form):

    url = forms.URLField(label='Url')


class SiteAddFormA(forms.ModelForm):
    url = forms.URLField(max_length=200, help_text='Please enter the URL of     the page.')

class Meta:
    model = Site
    fields = ('url', 'name', 'description',)

urls.py

urlpatterns = [
url(r'^$', views.index, name='index'),
url(r'^category/(?P<category_name_slug>[\w\-]+)/$', views.category,
    name='category'),
url(r'^category/(?P<category_name_slug>[\w\-]+)/(?P<subcategory_name_slug>[\w\-]+)/$',
    views.subcategory,
    name='subcategory'),
url(r'^category/(?P<category_name_slug>[\w\-]+)/(?P<subcategory_name_slug>[\w\-]+)/(?P<id>[\w\-]+)/$',
    views.site,
    name='site'),
url(r'^category/(?P<category_name_slug>[\w\-]+)/(?P<subcategory_name_slug>[\w\-]+)/add_site/$',
    views.add_site,
    name='add_site'),

]

models.py：

class Site(models.Model):
category = models.ForeignKey('Category')
subcategory = ChainedForeignKey(
    'Subcategory',
    chained_field='category',
    chained_model_field='category',
    show_all=False,
    auto_choose=True)
name = models.CharField(max_length=30)
description = models.TextField()
keywords = MyTextField()
date = models.DateTimeField(default=datetime.now)
url = models.URLField()

def __str__(self):
    return self.name