I've made a nice form, and a big complicated 'add' function for handling it. It starts like this...
def add(req):
if req.method == 'POST':
form = ArticleForm(req.POST)
if form.is_valid():
article = form.save(commit=False)
article.author = req.user
# more processing ...
Now I don't really want to duplicate all that functionality in the edit()
method, so I figured edit
could use the exact same template, and maybe just add an id
field to the form so the add
function knew what it was editing. But there's a couple problems with this
article.id
in the add
func? It would have to be after form.save
because that's where the article gets created, but it would never even reach that, because the form is invalid due to unique constraints (unless the user edited everything). I can just remove the is_valid
check, but then form.save
fails instead.So how do I deal with this?
If you are extending your form from a ModelForm, use the instance
keyword argument. Here we pass either an existing instance
or a new one, depending on whether we're editing or adding an existing article. In both cases the author
field is set on the instance, so commit=False
is not required. Note also that I'm assuming only the author may edit their own articles, hence the HttpResponseForbidden response.
from django.http import HttpResponseForbidden
from django.shortcuts import get_object_or_404, redirect, render, reverse
@login_required
def edit(request, id=None, template_name='article_edit_template.html'):
if id:
article = get_object_or_404(Article, pk=id)
if article.author != request.user:
return HttpResponseForbidden()
else:
article = Article(author=request.user)
form = ArticleForm(request.POST or None, instance=article)
if request.POST and form.is_valid():
form.save()
# Save was successful, so redirect to another page
redirect_url = reverse(article_save_success)
return redirect(redirect_url)
return render(request, template_name, {
'form': form
})
And in your urls.py
:
(r'^article/new/$', views.edit, {}, 'article_new'),
(r'^article/edit/(?P<id>\d+)/$', views.edit, {}, 'article_edit'),
The same edit
view is used for both adds and edits, but only the edit url pattern passes an id to the view. To make this work well with your form you'll need to omit the author
field from the form:
class ArticleForm(forms.ModelForm):
class Meta:
model = Article
exclude = ('author',)