Django Admin - Unable to change Foreign Key field

Question

I have Django version 1.4.5

Here are the relevant parts of my model

class Product (models.Model):
    name=models.CharField(max_length=200)
    description=models.TextField()
    label=models.ForeignKey('Label')
    pub_date = models.DateTimeField(editable=False)

    def save(self):
        #item will not have id if this is the first save
        if not self.id:
            self.pub_date = datetime.date.today()
            super(Product, self).save()

    def __unicode__(self):
    return self.name

class Label(models.Model):
    """
    A clothing label, e.g. Kate Spade
    """
    name=models.CharField(max_length=100)

    def __unicode__(self):
        return self.name

When I attempt to publish a Product, selecting a Label works fine. Publishing the item works as expected, and the label field remains populated upon returning to the Product in the admin console. However, if I attempt to change the value of the label field, I am taken to the default list of Products page, with the message "he product "Prod 1" was changed successfully" but returning to the Prod 1 page reveals that the field wasn't actually saved properly.

Any ideas here?

Answer 1

super(Product, self).save() is within the if block, so it isn't being called on edits. Also, why not just use auto_now_add on the pub_date field?

Answer 2

In your case, no need to set the date & time explicitly. You can use ' auto_now_add ' Please fer this link for more details.

https://docs.djangoproject.com/en/dev/ref/models/fields/#django.db.models.DateField.auto_now_add

class Product (models.Model):
    name=models.CharField(max_length=200)
    description=models.TextField()
    label=models.ForeignKey('Label')
    pub_date = models.DateTimeField(editable=False, auto_now_add = True)

    def __unicode__(self):
    return self.name

If you need to set it manually, Use the following snippet. It calls super class for change also.

def save(self):
    #item will not have id if this is the first save
    if not self.id:
        self.pub_date = datetime.date.today()
    super(Product, self).save()