如何将嵌套类别添加到Django模型？

Question

What I am trying to achieve is to design a model which has nested levels of categories.

the levels are like this.

category0 > category1 > category2 > category3 > category4 > category5

Posts can have levels from 0 - 5 , so a post can have category 0 - 1 , while other post may have 0 - 4 or 0 - 5 ,

The category on the given highest level ( 0 is the lower while 5 is the highest) should inherit from the one just below it, ( 1 > 2 > 3 > 4 > 5 )

How can I achive this?

My current categories looks like this

class Category0(models.Model):
    name = models.CharField(max_length=50, unique=True)
    slug = models.SlugField(max_length=60)


class Category1(models.Model):
    name = models.CharField(max_length=50, unique=True)
    slug = models.SlugField(max_length=60)
    parent = models.ForeignKey(Category0)


class Category2(models.Model):
    name = models.CharField(max_length=50, unique=True)
    slug = models.SlugField(max_length=60)
    parent = models.ForeignKey(Category1)


class Category3(models.Model):
    name = models.CharField(max_length=50, unique=True)
    slug = models.SlugField(max_length=60)
    parent = models.ForeignKey(Category2)


class Category4(models.Model):
    name = models.CharField(max_length=50, unique=True)
    slug = models.SlugField(max_length=60)
    parent = models.ForeignKey(Category3)


class Category5(models.Model):
    name = models.CharField(max_length=50, unique=True)
    slug = models.SlugField(max_length=60)
    parent = models.ForeignKey(Category4)

And the post model here

class Product(models.Model):
    title = models.CharField(max_length=20)
    slug = AutoSlugField(unique=True, populate_from='title')
    content = models.TextField(blank=True)
    category = models.ForeignKey(CategoryChild4)

What would be the best method? any suggestions or changes welcome.

Update

The backend is PostgrSQL.

Thanks

Answer 1

Could you use a Foreign Key to self approach?

For example:

class Category(models.Model):

    parent = models.ForeignKey('self', default=None, null=True, blank=True, related_name='nested_category')
    nesting_level = models.IntegerField()
    name = models.CharField(max_length=50, unique=True)
    slug = models.SlugField(max_length=60)

It's probably useful to keep track of the nesting levels explicitly with nesting_level but this way you can create the relationship you describe.

Answer 2

If you are using Postgres as your database, I probably would not take this approach. I would look into using the new json datatype (postgres 9.3>). If you want to utilize this you can store this type of information in document form (think mongo-db but in an RDBMS). I recommend installing this field:

https://github.com/bradjasper/django-jsonfield/

The only downside is that you need to perform validation yourself, but since this a multiple layered model, you would probably need to do that anyway based on the way you are doing it above.

You could look into using MongoDB also....