Django：相同的 model 具有不同的功能？

Question

Object Model:

class Object(models.Model):
    author = models.ForeignKey(ProfileUser, on_delete=models.CASCADE)
    title = models.CharField(max_length=300)
    category = models.ForeignKey(Category, on_delete=models.CASCADE)
    address = models.CharField(max_length=300)
    content = models.TextField()
    created_date = models.DateTimeField(default=timezone.now)
    approved_object = models.BooleanField(default=False)
    admin_seen = models.BooleanField(default=False)

    def __str__(self):
        return f"{self.title}"

Category model:

class Category(models.Model):
    title = models.CharField(max_length=50)

    def __str__(self):
        return f"{self.title}"

For example I have some categories, like hotels, restaurants etc. So I want for each category to have different features (radio buttons when adding new), but I'm not sure, how to handle it properly. Hotels must have rooms, pool etc. Restaurants must have country kitchen, seats etc. In future I will have and other categories.

Quesion is: Which is the best way (practice) to do this.

My solution: To create third table with features and every category to have column features and store features separate by comma, but it's not very good solution based on DB normalization .

Answer 1

You could use abstract base classes :

Abstract base classes are useful when you want to put some common information into a number of other models. You write your base class and put abstract=True in the Meta class. This model will then not be used to create any database table. Instead, when it is used as a base class for other models, its fields will be added to those of the child class.

You can then make your Restaurant and Hotel models inherit from this abstract class. Django will then create two tables with the base fields from the abstract class plus the specific fields from each models.

Answer 2

You can use multi-table inheritance

You define a base object, and from there you can define different child objects which will share the parent's properties

In your case that would look something like this:

class Object(models.Model):
    ...


class Restaurant(Object):
   seats = IntegerField(...)
   reservations = ManyToManyField(...)

class Hotel(Object):
   rooms = IntegerField(...)
   has_pool = BooleanField(...)

Django will automatically create relationships and manage the querying for you. To get all restaurants, you can use Restaurant.objects.all() , there is a limitation though. When querying Object.objects.all() , you will get a list of the Objects , not their specific subclass. If I remember correctly, you can access the specific instance through (for instance) object.restaurant .

If you do want to get the specific objects, you can look into a library called Django-polymorphic .

Answer 3

i will explain this one by one:

• category table contains all categories.
• now there may have some common and unique feature for every category. features will have many to many relation with category table.
  so we create feature_master table and we will map it with category table.
• feature_master table contains all features.
• category_feature_map table is map table(junction table)
• object table have all the detail about object and object_detail table will contain all the feature to particular object