Django unique slug field for two or more models-CodePudding

I have such structure:

class Category(models.Model):
    name = models.CharField(max_length=255, validators=[MinLengthValidator(3)])
    parent = models.ForeignKey('self', blank=True, null=True,
                               related_name='children',
                               on_delete=models.CASCADE
                               )
    slug = models.SlugField(max_length=255, null=False, unique=True)


class Product(models.Model):
    name = models.CharField(max_length=255, validators=[MinLengthValidator(3)])
    to_category = models.ForeignKey(Category, on_delete=models.SET_NULL,
                                    blank=True, null=True,
                                    )
    slug = models.SlugField(max_length=255, null=False, unique=True)

I have created one category with slug "test". When I try to create new category with slug "test" I got warning message and it is Ok. But If I try to create product with slug "test" I dont have warning and this is not good in my case. Is there a solution or method to validate slug field for uniqueness with Product and Category model?

CodePudding user response：

You can override the save method for each, and then check if the given slug already exists for a product or category.

def is_slug_unique(slug):
    product_exists = Product.objects.filter(slug=slug).exists()
    category_exists = Category.objects.filter(slug=slug).exists()
    if product_exists or category_exists:
        return False
    else:
        return True

class Category(models.Model)
    ...

    def save(self, *args, **kwargs):
        slug_unique = is_slug_unique(self.slug)
        if not slug_unique:
            # do something when the slug is not unique
        else:
            # do something when the slug is unique
            super().save(*args, **kwargs)

class Product(models.Model)
    ...

    def save(self, *args, **kwargs):
        slug_unique = is_slug_unique(self.slug)
        if not slug_unique:
            # do something when the slug is not unique
        else:
            # do something when the slug is unique
            super().save(*args, **kwargs)

CodePudding user response：

An idea might be to create a Slug model that stores all the slugs, optionally with a backreference to the object:

class Slug(models.Model):
    slug = models.SlugField(max_length=255, primary_key=True)

Then the slugs in your models are ForeignKeys to that Slug model, and you check if such slug already exists:

from django.core.exceptions import ValidationError


class Product(models.Model):
    name = models.CharField(max_length=255, validators=[MinLengthValidator(3)])
    to_category = models.ForeignKey(
        Category, on_delete=models.SET_NULL, blank=True, null=True
    )
    slug = models.ForeignKey(Slug, on_delete=models.PROTECT)

    def validate_slug(self):
        if self.pk is not None and Slug.objects.filter(pk=self.slug_id).exclude(
            product__pk=self.pk
        ):
            raise ValidationError('The slug is already used.')

    def clean(self, *args, **kwargs):
        self.validate_slug()
        return super().clean(*args, **kwargs)

    def save(self, *args, **kwargs):
        self.validate_slug()
        return super().save(*args, **kwargs)

That being said, often overlapping slugs for different entity types are allowed.