Django Form If condition in view.py with 2 instance

问题

TO SAVE DATA that is inputted in form in Django i tried tomake it like this I put this in my model.py

class Item(models.Model):
    CATEGORY = (
        ('Gudang Kering', 'Gudang Kering'),
        ('Gudang Basah','Gudang Basah'),
        )
    name = models.CharField(max_length=200,null= True)
    stock = models.IntegerField(default='0', blank=False, null=True)
    category = models.CharField(max_length=200,null= True,choices=CATEGORY)
    reorderlevel = models.IntegerField(default='0', blank=False, null=True)
    maxreorderlevel = models.IntegerField(default='0', blank=False, null=True)
    description = models.CharField(max_length=200,null= True, blank= True)
    date_created = models.DateTimeField(auto_now_add= True)
    tags = models.ManyToManyField(Tag)
    
    def __str__(self):
        return self.name

class Issue(models.Model):
    STATUS = (
        ('Pending', 'Pending'),
        ('Granted','Granted'),
        ('Denied','Denied'),
        )
    customer = models.ForeignKey(Customer, null=True, on_delete= models.SET_NULL)
    item = models.ForeignKey(Item, null=True, on_delete= models.SET_NULL)
    quantity = models.IntegerField(default='0', blank=False, null=True)
    date_created = models.DateTimeField(auto_now_add=True, auto_now=False)
    status = models.CharField(max_length=200,null= True, choices=STATUS)

Then in view.py i define the form like this

def updateIssue(request, pk):
    issue = Issue.objects.get(id=pk)
    item = Item.objects.all()
    form = UpdateIssueForm(instance=issue)
    if request.method == 'POST':
        form = UpdateIssueForm(request.POST,instance=issue)
        #print ('printing:',request.POST)
        if form.is_valid():
            instance = form.save(commit=False)
            if instance.status == 'Granted':
                item.stock -= instance.quantity
                instance.save()
                item.save()
            else:
        instance.save()

        return redirect('/')
    

    context = {'form':form}
    return render(request,'accounts/issue_form.html',context)``

The Goal
if instance == "Granted"
the item.stock will be decreased on the amount of instance.quantity and will be saved.
else
instance will just be saved without affecting the stock from the 2nd model

The error

    item = Item.objects.all()

even when called the item.stock have 0 attribute even when i have input data in database for that table

来源：https://stackoverflow.com/questions/63043875/django-form-if-condition-in-view-py-with-2-instance