级联下拉的实现方式（如省市县）-1 Smart Selects方式

https://django-smart-selects.readthedocs.io/en/latest/usage.html

特点： 简单，不容易定制，适合简单的关联下拉，只能是table-table

有单选、多选、guoup分组等3种组合

from django.db import models
from smart_selects.db_fields import (  ChainedForeignKey,    ChainedManyToManyField,    GroupedForeignKey,
)

class Continent(models.Model):
    name = models.CharField(max_length=255)
    def __str__(self):
        return "%s" % self.name

class Country(models.Model):
    continent = models.ForeignKey(Continent, on_delete=models.CASCADE)
    name = models.CharField(max_length=255)
    def __str__(self):
        return "%s" % self.name


class Location(models.Model):

    continent = models.ForeignKey(Continent, on_delete=models.CASCADE)
    country = ChainedForeignKey(
        "Country",
        chained_field="continent",
        chained_model_field="continent",
        show_all=False,
        auto_choose=True,
        null=True,
        blank=True
    )
    city = models.CharField(max_length=50)
    street = models.CharField(max_length=100)

我在录入location时候， 选择 contient，根据大陆筛选country

关键代码：

class LocationForm(forms.ModelForm):
    class Meta:
        model = Location
        fields = '__all__'
    def clean(self):
        cleaned_data = super().clean()

locationCreate.html

{% extends 'appsmarts/base.html' %}
{% load crispy_forms_tags %}
{% load static %}

{% block content %}

<form action='.' method='POST'>{% csrf_token %}
    <script src="{% static 'js/jquery-3.3.1.min.js' %}"></script>
    <script src="{% static 'smart-selects/admin/js/bindfields.js' %}"></script>
    <script src="{% static 'smart-selects/admin/js/chainedfk.js' %}"></script>
    {{ form|crispy}}
    <input type='submit' value='Save' />
</form>

{% endblock %}

js必须放在form tab里面，不知为什么。

smartSelect lib用的js,调用的是google cdb，组好复制到本地，改掉

总之，容易用，但是限制太多 1.只能table-table  2.根据权限不好筛选