【Django】最新の年齢を取得し続ける2つの方法

from django.utils import timezone

class Child(models.Model):
    # 生年月日
    birthdate = models.DateField(
        verbose_name="生年月日",
        blank=True,
        null=True,
    )

    @property
    def age(self):
        # 今日の日付を取得
        today = timezone.now().date()
        # 年齢を計算
        age = today.year - self.birthdate.year
        # 誕生日が来ていない場合は1引く
        if (today.month, today.day) < (self.birthdate.month, self.birthdate.day):
            age -= 1
        return age

# 例: Childインスタンスのageプロパティにアクセス
child = Child.objects.get(id=1)
# メソッド呼び出しではなく、属性としてアクセス
print(child.age)

from django.conf import settings
from django.db import models
from django.core.validators import MinValueValidator


class Child(models.Model):    
    # 年齢
    age = models.PositiveIntegerField(
        blank=True,
        null=True,
        validators=[MinValueValidator(0)],
        help_text="子供の年齢（自動更新されます）",
    )

from django.core.management.base import BaseCommand
from django.utils import timezone
from myapp.models import Child

class Command(BaseCommand):
    help = "Update ages for all children"

    def handle(self, *args, **kwargs):
        today = timezone.now().date()
        children = Child.objects.filter(birthdate__isnull=False)
        for child in children:
            age = today.year - child.birthdate.year
            if (today.month, today.day) < (child.birthdate.month, child.birthdate.day):
                age -= 1
            child.age = age
            child.save()
        self.stdout.write(self.style.SUCCESS("Successfully updated ages"))

def clean(self):
    if self.age and self.age < 5:
        raise ValidationError("5歳未満の子供は登録できません。")