Dica 19.4 - Modelagem - Abstract Inheritance - Herança Abstrata

# backend/crm/models.py
from django.db import models


class Person(models.Model):
    first_name = models.CharField('nome', max_length=100)
    last_name = models.CharField('sobrenome', max_length=255, null=True, blank=True)  # noqa E501
    email = models.EmailField('e-mail', max_length=50, unique=True)

    class Meta:
        abstract = True
        ordering = ('first_name',)

    @property
    def full_name(self):
        return f'{self.first_name} {self.last_name or ""}'.strip()

    def __str__(self):
        return self.full_name


class Customer(Person):
    linkedin = models.URLField(max_length=255, null=True, blank=True)
    tags = models.TextField(null=True, blank=True)

    class Meta:
        verbose_name = 'cliente'
        verbose_name_plural = 'clientes'


class Seller(Person):
    internal = models.BooleanField('interno', default=True)
    commission = models.DecimalField('comissão', max_digits=7, decimal_places=2, default=0)  # noqa E501

    class Meta:
        verbose_name = 'vendedor'
        verbose_name_plural = 'vendedores'

# backend/crm/admin.py
from django.contrib import admin

from .models import Customer, Seller


@admin.register(Customer)
class CustomerAdmin(admin.ModelAdmin):
    list_display = ('__str__', 'email', 'linkedin')
    search_fields = ('first_name', 'last_name', 'email')


@admin.register(Seller)
class SellerAdmin(admin.ModelAdmin):
    list_display = ('__str__', 'email', 'internal', 'commission')
    search_fields = ('first_name', 'last_name', 'email')
    list_filter = ('internal',)

python manage.py makemigrations
python manage.py migrate

Migrations for 'crm':
  backend/crm/migrations/0001_initial.py
    - Create model Customer
    - Create model Seller
...
  Applying crm.0001_initial... OK

# backend/core/models.py
from django.db import models
from django.db.models.signals import post_save
from django.dispatch import receiver

from backend.accounts.models import User


class TimeStampedModel(models.Model):
    created = models.DateTimeField(
        'criado em',
        auto_now_add=True,
        auto_now=False
    )
    modified = models.DateTimeField(
        'modificado em',
        auto_now_add=False,
        auto_now=True
    )

    class Meta:
        abstract = True


class Profile(models.Model):
    ...

# backend/crm/models.py
from django.db import models

from backend.core.models import TimeStampedModel


class Person(models.Model):
    ...


class Customer(Person, TimeStampedModel):
    ...


class Seller(Person, TimeStampedModel):
    ...

python manage.py makemigrations

It is impossible to add the field 'created' with 'auto_now_add=True' to customer without providing a default. This is because the database needs something to populate existing rows.
 1) Provide a one-off default now which will be set on all existing rows
 2) Quit and manually define a default value in models.py.
Select an option: 1
Please enter the default value as valid Python.
Accept the default 'timezone.now' by pressing 'Enter' or provide another value.
The datetime and django.utils.timezone modules are available, so it is possible to provide e.g. timezone.now as a value.
Type 'exit' to exit this prompt
[default: timezone.now] >>>

Migrations for 'crm':
  backend/crm/migrations/0002_customer_created_customer_modified_seller_created_and_more.py
    - Add field created to customer
    - Add field modified to customer
    - Add field created to seller
    - Add field modified to seller

python manage.py migrate

python manage.py seed crm --number=5

Seeding 5 Customers
Seeding 5 Sellers
Model Customer generated record with primary key 1
...
Model Seller generated record with primary key 5

python manage.py shell_plus

Customer.objects.all()
# <QuerySet [<Customer: Justin Farley>, <Customer: Shari Morales>, <Customer: Timothy Prince>, <Customer: Jennifer Morales>, <Customer: John Hill>]>

sellers = Seller.objects.all()

for seller in sellers:
    print(seller.first_name, seller.created)

Bryan 2008-09-13 20:06:49+00:00
Patrick 2005-07-15 22:12:00+00:00
Heather 2000-02-14 10:39:39+00:00
Kelly 1990-02-16 17:26:53+00:00
Stephanie 1998-01-03 06:16:29+00:00

from time import sleep

names = ['Huguinho', 'Zezinho', 'Luizinho']

for name in names:
    Seller.objects.create(
        first_name=name,
        last_name='Donald',
        email=f'{name.lower()}@email.com'
    )
    sleep(1.2)  # Só um testezinho de delay

sellers = Seller.objects.filter(last_name='Donald')

for seller in sellers:
    print(seller.first_name, seller.created)

Huguinho 2022-12-19 16:09:37.591917+00:00
Zezinho 2022-12-19 16:09:38.804876+00:00
Luizinho 2022-12-19 16:09:40.016960+00:00

class Customer(Person, TimeStampedModel):
    ...

    class Meta(Person.Meta):
        verbose_name = 'cliente'
        verbose_name_plural = 'clientes'