Question

I am trying to change a form’s instance before I save it. I need to set certain information within the view like this:

 class UploadedFile(models.Model):

     file = models.FileField(storage=s3store, upload_to=custom_upload_to)
     slug = models.SlugField(max_length=50, blank=True)
     bucket = models.ForeignKey(S3Bucket, blank=False)
     uploaded_by = models.ForeignKey(User, related_name='uploaded_by', blank=False)
     company = models.ForeignKey(Company, blank=False)

—

class UploadForm(ModelForm):

    class Meta:
        model = UploadedFile    

—

form = UploadForm(request.POST, request.FILES)
form.instance.company_id = r_user.company.id
form.instance.uploaded_by_id = r_user.id
form.instance.bucket_id = r_user.company.s3_bucket_id
if form.is_valid():
     form_object = form.save()

Now, I get that the form is not valid because company/uploaded/bucket are empty:

Errors Form:

company

This field is required.

bucket

This field is required.

uploaded_by

This field is required.

But I did set them! Do I need to make them blank=True, then do a save(commit=false), change them, and then resave? If yes, why is so? I did change the form ….

Answer 1

The assignments are late. In the __init__() of ModelForm, or in your code: the form = UploadForm(request.POST, request.FILES) line, an instance has been created and populated to initial of the form. Later modification upon the instance will not affect the value of form.initial.

Also, if you want to fill in some fields automatically in backend, don’t render them to user.

Thus, yes, you could make them blank=True or exclude them from the form then follow the suggested way.