Django: Check if a object exists but isn't current instance of object

Question

I've put together a basic CMS system for a project and I'm adding an order system so that you can order the created pages in the nav bar. Unfortunately the custom validator I've written is a little to aggressive and raises and error when you edit a page because, correctly, the order already exists in the database.

Model the form is based on:

class Page(models.Model):
page_name = models.CharField(max_length=100)
page_content = models.CharField(max_length=16777000)
link = models.URLField(blank=True)
order = models.IntegerField()

Custom Validator:

def clean_order(self):
    data = self.cleaned_data['order']
    pg = Page.objects.filter(order=data)
    if pg.count() > 0:
        raise forms.ValidationError("This order number already exists. Use another.")
    return data

Is there any way for me to, upon performing the update, have the custom validator only raise an error if the new order already exists BUT where it is not current Page object. Something like:

pg = Page.objects.filter(order=data).filter(pk!=editpagepk)

Thanks!

girasquid · Accepted Answer · 2013-02-07 22:01:26Z

3

Use the exclude method, like so:

pg = Page.objects.filter(order=data).exclude(pk=self.instance.pk)

answered Feb 7, 2013 at 22:01

girasquid

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Community · Accepted Answer · 2017-05-23 12:27:02Z

1

Use Django queryset's exclude to exclude the current object from the results. Assuming you have an id field in the Page model acting as a primary key:

def clean_order(self):
    order = self.cleaned_data['order']
    pg = Page.objects.filter(order=order).exclude(id=self.instance.id)
    if pg.count() > 0:
        raise forms.ValidationError(" ... ")
    return data

The above assumes you're using a ModelForm, because that's what you need to find the current object instance being submitted via POST at self.instance. More details about this last point here.

edited May 23, 2017 at 12:27

CommunityBot

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answered Feb 7, 2013 at 22:04

Joseph Victor Zammit

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Comments

Daniel · Accepted Answer · 2015-01-23 18:23:33Z

0

I guess you could try to query the matching object and catch the exception:

try:
    Page.objects.filter(order=data).get(pk=editpagepk)
except Page.DoesNotExist:
    raise forms.ValidationError("...")

answered Jan 23, 2015 at 18:23

Daniel

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