IntegrityError NOT NULL constraint failed

Question

I'm building a simple blog app using Django. I want to realize the function of adding a new blog using form. Some problems occurs.

Here is my models.py

from django.db import models
from django.utils import timezone
from django.template.defaultfilters import slugify
from django.contrib.auth.models import User

class Blog(models.Model):
    title=models.CharField(max_length=60)
    content=models.TextField()
    author=models.ForeignKey('auth.User',on_delete=models.CASCADE,)
    date=models.DateTimeField(default=timezone.now)
    slug=models.SlugField(null=True,unique=True)

    def save(self, *args, **kwargs):
      self.slug = slugify(self.title)
      super(Blog, self).save(*args, **kwargs)

    def __str__(self):
        return self.title

class UserProfile(models.Model):
    user=models.OneToOneField(User)
    website=models.URLField(blank=True)

    def __str__(self):
        return self.user.username   

forms.py

 from django.template.defaultfilters import slugify
 from blog.models import UserProfile
 from django.contrib.auth.models import User

 class BlogForm(forms.ModelForm):
     title=forms.CharField(max_length=60,
                      help_text="blog title")
     content=forms.CharField(help_text="blog content")
     author=forms.CharField(help_text="blog author")
     date=forms.DateTimeField(help_text="blog date")

     class Meta:
         model=Blog
         fields=('title',)
 class UserForm(forms.ModelForm):
     password = forms.CharField(widget=forms.PasswordInput())

     class Meta:
         model=User
         fields = ('username','email','password')
 class UserProfileForm(forms.ModelForm):
     class Meta:
         model=UserProfile
         fields=('website',)

the add_blog method in views.py

def add_blog(request):    
form=BlogForm()    
if request.method =='POST':
    form=BlogForm(request.POST)
    if form.is_valid():
        form.save(commit=True)
        return index(request)
    else:
        print(form.errors)

return render(request, 'add_blog.html',{'form':form})

When I want to add a new blog in my webpage, I can't input the record. It shows me

IntegrityError at /add_blog/
NOT NULL constraint failed: blog_blog.author_id

Could anybody help me fix this problem? Thanks a lot!

Answer 1

In your models, your Blog class requires:

1. Title
2. An author, of type auth.User
3. content

The first step, is to remove the author field from your form:

class BlogForm(forms.ModelForm):
     title=forms.CharField(max_length=60,
                      help_text="blog title")
     content=forms.CharField(help_text="blog content")
     # author=forms.CharField(help_text="blog author")
     date=forms.DateTimeField(help_text="blog date")

     class Meta:
         model=Blog
         fields=('title','content','date')

Next, is to add the logged in user as the author in your view:

from django.shortcuts import redirect
from django.contrib.auth.decorators import login_required

# makes sure this view is called with a valid user
# https://docs.djangoproject.com/en/2.0/topics/auth/default/#the-login-required-decorator
@login_required
def add_blog(request):    
   form = BlogForm(request.POST or {})    
   if form.is_valid():
        temp = form.save(commit=False)
        temp.author = request.user # add the logged in user, as the
                                   # author
        temp.save()
        return redirect('/')
   return render(request, 'add_blog.html',{'form':form})

Answer 2

Another way to view this problem... Perhaps you can Try clearing your migration files , and re-run makemigrations to see if it catches anything off about your models. It may ask you for a default value for some of the fields; and this should ring a bell to assign null=True where appropriate. Personally this is quite a common integrity conflict for me (i'm new to the framework) especially when i've done many unplanned on the fly mods to models on the same db.