Python Django: "Post.author" must be a "User" instance

Question

When I try to assign an author, or user to a Post, Django spews out the following error:

Cannot assign "<User: henrydavidzhu>": "Post.author" must be a "User" instance.

Here is my views.py:

user_passes_test(lambda u: u.is_authenticated)
def add_post(request):
    form = PostForm(request.POST or None)

    print("User: " + str(request.user))

    if form.is_valid() and request.user.is_authenticated():
        post = form.save(commit=False)
        post.author = request.user
        post.save()
        return redirect(post)
    else:
        print(form.errors)

    return render_to_response('webapp/startthread.html', 
                              { 'form': form },
                              context_instance=RequestContext(request))

And here is my forms.py:

class PostForm(forms.ModelForm):
    CHOICES = (
        ('Hardware and OS', '&nbsp;&nbsp;&nbsp;&nbsp;Desktops'),
    )
    field = forms.ChoiceField(choices=CHOICES)

    class Meta:
        model = Post
        exclude = ['author', 'slug']

And here is my models.py:

class Post(models.Model):
    title = models.CharField(max_length=500)
    slug = models.SlugField(unique=True)
    text = models.TextField()
    created_on = models.DateTimeField(auto_now_add=True)
    author = models.ForeignKey(User, unique=True)

    def __unicode__(self):
        return self.title

    @models.permalink
    def get_absolute_url(self):
        return ('blog_post_detail', (), 
                {
                    'slug' :self.slug,
                })

    def save(self, *args, **kwargs):
        if not self.slug:
            self.slug = slugify(self.title)
        super(Post, self).save(*args, **kwargs)

That's the reason then; `Post.author` has to be a `User` object, just as the error message said. — John Gordon, Apr 05 '16 at 18:59
likely because of `author = models.ForeignKey(User, unique=True)` — nathan.medz, Apr 05 '16 at 18:59
If you want to keep that foreign key reference then you need it to be an instance of the user object as @JohnGordon suggested — nathan.medz, Apr 05 '16 at 19:02
Possible duplicate of [django: Purpose of django.utils.functional.SimpleLazyObject?](http://stackoverflow.com/questions/10506766/django-purpose-of-django-utils-functional-simplelazyobject) — Shang Wang, Apr 05 '16 at 19:03
Don't forget to call the `is_authenticated` method in your lambda function, i.e. `u.is_authenticated()`. Otherwise it will always evaluate to `True`! In this case, you could use `login_required` instead of `user_passes_test`. — Alasdair, Apr 05 '16 at 19:27

score 0 · Answer 1 · answered Apr 05 '16 at 19:06

0

I had to change the following:

author = models.ForeignKey(User)

to this:

author = models.ForeignKey('auth.User')

answered Apr 05 '16 at 19:06

Henry Zhu

2,488
9
43
87

Arun V Jose · Accepted Answer · 2017-06-09T17:56:18.743

0

I am using django 1.8 and your code is work for me. if your site is login, request.user give the User instance for example:

print request.user

edited Jun 09 '17 at 17:56

answered Apr 06 '16 at 03:37

Arun V Jose

3,321
2
24
24

Python Django: "Post.author" must be a "User" instance

2 Answers2