Django 错误：类型 object 'Invoice_Line' 没有属性 'objects'

Question

I defined a method in admin.py to add up after-tax amounts:

def _grand_total(self, object_id):
        line_amounts = Invoice_Line.objects.filter(appointment_ref=object_id).values_list('total_after_tax', flat=True)
        return reduce((lambda x,y: x + y), line_amounts)

The ORM query defined in this line: Invoice_Line.objects.filter(appointment_ref=object_id).values_list('total_after_tax', flat=True)

generates the error below:

type object 'Invoice_Line' has no attribute 'objects'

Models code shown below:

models.py:

class Appointment(models.Model):
    create_date = models.DateField(auto_now_add=True, db_index=True)
    appointment_ref = models.AutoField(primary_key=True)
    appointment_date = models.DateField()

class Invoice_Line (models.Model):
    appointment_ref = models.ForeignKey(Appointment, on_delete=models.CASCADE)
    inv_line_date = models.DateTimeField(auto_now_add=True)
    item_price = models.DecimalField(max_digits=7, decimal_places=2, default=00000.00, verbose_name='Service Amount')
    tip_amount = models.DecimalField(max_digits=7, decimal_places=2, default=00000.00, verbose_name='Tip Amount')
    item_quantity = models.PositiveSmallIntegerField(blank=False, null=True, default=0, verbose_name='Service Quantity')
    total_before_tax = models.DecimalField(max_digits=7, decimal_places=2, default=00000.00, verbose_name='Before Tax')
    stax_rate = models.DecimalField(max_digits=5, decimal_places=4, blank=True, null=True, verbose_name='Sales Tax Rate')
    stax_amount = models.DecimalField(max_digits=7, decimal_places=2, default=00000.00, verbose_name='Sales Tax Amount')
    total_after_tax = models.DecimalField(max_digits=7, decimal_places=2, default=00000.00, verbose_name='Total After Tax')

I run the same query in the shell/interpreter, and it works just fine. Can I get assistance in fixing this error?

Any help will be appreciated!

Thanks!

Answer 1

Fixed the issue:

As I mentioned in my question, I had defined the method below in admin.py:

def _grand_total(self, object_id):
        line_amounts = Invoice_Line.objects.filter(appointment_ref=object_id).values_list('total_after_tax', flat=True)
        return reduce((lambda x,y: x + y), line_amounts)

And I had also registered "Invoice_Line" model in admin.py as shown below:

@admin.register (Invoice_Line)
class Invoice_Line(admin.ModelAdmin):
    list_display = ('__str__','inv_line_date','total_after_tax','appointment_ref')
    readonly_fields = ('item_price','total_before_tax','stax_rate','stax_amount','total_after_tax')

The problem was that you can't name the class you use to register a model in admin.py exactly the same as how you named the model in models.py.

In other words you can't do this:

models.py:

class Invoice_Line (models.Model):
    ......
    ......

admin.py:

@admin.register (Invoice_Line)
class Invoice_Line (admin.ModelAdmin):
    .......
    .......

Once I changed the name of the class in admin.py to " class InvoiceLineAdmin (admin.ModelAdmin): " the ORM query originating the error I was trying to fix worked just fine.