我正在使用 django 和 postgresql。我正在处理一个三向依赖下拉列表。添加国家选择后，省区将根据所选国家自动更新。选择一个省后，只有在刷新页面时才会打开县字段。如果你在这方面帮助我，我会很高兴。

模型.py

from django.db import models

class Country(models.Model):
    name = models.CharField(max_length=30)

    def __str__(self):
        return self.name

class City(models.Model):
    country = models.ForeignKey(Country, on_delete=models.CASCADE)
    name = models.CharField(max_length=30)

    def __str__(self):
        return self.name

class District(models.Model):
    city = models.ForeignKey(City, on_delete=models.CASCADE)
    name = models.CharField(max_length=30)

    def __str__(self):
        return self.name

class Person(models.Model):
    name = models.CharField(max_length=100)
    birthdate = models.DateField(null=True, blank=True)
    country = models.ForeignKey(Country, on_delete=models.SET_NULL, null=True)
    city = models.ForeignKey(City, on_delete=models.SET_NULL, null=True)
    district = models.ForeignKey(District, on_delete=models.SET_NULL, null=True)

    def __str__(self):
        return self.name

表格.py

from django import forms
from .models import …