Python Django form组件动态从数据库取choices数据的方式

from django.db import models
 
class UserInfo(models.Model):
  username = models.CharField(max_length=16)
  password = models.CharField(max_length=16)
  mobile = models.CharField(max_length=11)
 
class City(models.Model):
  name = models.CharField(max_length=16, null=False, unique=True)

from django.shortcuts import render, HttpResponse
from app01 import models
 
from django import forms
from django.forms import widgets
from django.core.validators import RegexValidator
from django.core.exceptions import ValidationError
 
 
class RegForm(forms.Form):
  username = forms.CharField(
    min_length=5,
    label="用户名",
    error_messages={
      "min_length": "用户名不能小于5位！",
      "required": "该字段不能为空"
    },
    widget=widgets.TextInput(attrs={"class": "form-control"})
  )
 
  password = forms.CharField(
    min_length=6,
    label="密码",
    error_messages={
      "min_length": "密码不能少于6位！",
      "required": "该字段不能为空"
    },
    widget=widgets.PasswordInput(attrs={"class": "form-control"}, render_value=True)
  )
 
  re_password = forms.CharField(
    min_length=6,
    label="确认密码",
    error_messages={
      "required": "该字段不能为空"
    },
    widget=widgets.PasswordInput(attrs={"class": "form-control"}, render_value=True)
  )
 
  mobile = forms.CharField(
    label="手机号",
    # 自定义正则匹配规则
    validators=[
      RegexValidator(r'^[0-9]+$', "手机号必须是数字"), # 判断手机号是否为数字
      RegexValidator(r'^1[3-9][0-9]{9}$', "手机格式有误") # 判断手机号是否为 1 和 3-9 开头的十一位数
    ],
    error_messages={
      "required": "该字段不能为空",
    },
    widget=widgets.TextInput(attrs={"class": "form-control"})
  )
 
  city = forms.ChoiceField(
    choices=models.City.objects.values_list("id", "name"),
    label="城市",
    initial=2,
    widget=widgets.Select()
  )
 
  # 重写父类的 __init__ 方法
  def __init__(self, *args, **kwargs):
    super().__init__(*args, **kwargs)
    self.fields['city'].widget.choices = models.City.objects.values_list("id", "name")
 
  # 判断用户名信息
  def clean_username(self):
    value = self.cleaned_data.get("username")
    if "admin" in value:
      raise ValidationError("用户名不能含有敏感信息")
 
  # 重写父类的 clean 方法
  def clean(self):
    password = self.cleaned_data.get("password")
    re_password = self.cleaned_data.get("re_password")
    if re_password != password:
      self.add_error("password", ValidationError("两次密码不一致"))
      self.add_error("re_password", ValidationError("两次密码不一致"))
      raise ValidationError("两次密码不一致")
    return self.cleaned_data
 
 
def reg2(request):
  form_obj = RegForm() # GET 请求
 
  if request.method == "POST":
    form_obj = RegForm(request.POST)
    # 让 form 来帮我们进行校验
    if form_obj.is_valid():
      # 如果通过校验
      # 所有经过校验的数据都保存在 form_obj.cleaned_data
      print(form_obj.cleaned_data)
      models.UserInfo.objects.create(**form_obj.cleaned_data)
      return HttpResponse("注册成功")
 
  return render(request, "reg2.html", {"form_obj": form_obj})