facturio/subjects/models.py

from django.db import models
from django.utils.translation import gettext_lazy as _


class Subject(models.Model):
    class Meta:
        verbose_name = _('Subject')
        verbose_name_plural = _('Subjects')

    id = models.CharField(_('CIN'), max_length=8, primary_key=True)
    vat_id = models.CharField(
        _('VAT ID'),
        max_length=12,
        null=True,
        blank=True,
    )

    def get_latest_data(self):
        return (
            self.subject_data.filter(subject=self)
            .order_by(
                '-created_date',
            )
            .first()
        )

    def __str__(self):
        return f'{self.id} - {self.get_latest_data().name}'


class SubjectData(models.Model):
    class Meta:
        verbose_name = _('Subject Data')
        verbose_name_plural = _('Subject Datas')

    subject = models.ForeignKey(
        Subject,
        on_delete=models.CASCADE,
        related_name='subject_data',
    )
    name = models.CharField(_('Name'), max_length=128)
    street = models.CharField(_('Street'), max_length=64)
    zip_code = models.CharField(_('Zip Code'), max_length=6)
    city = models.CharField(_('City'), max_length=64)
    city_part = models.CharField(
        _('City part'),
        max_length=64,
        null=True,
        blank=True,
    )
    created_date = models.DateTimeField(_('Created date'), auto_now_add=True)

    def __str__(self):
        return f'{self.subject.id} - {self.name} - {self.created_date}'